diff --git a/pyproject.toml b/pyproject.toml
index 06fbe913..342512a4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -9,6 +9,7 @@ dependencies = []
 [dependency-groups]
 dev = [
     "mypy==2.3.1",
+    "pytest>=9.1.1",
     "ruff==0.16.8",
 ]
 
diff --git a/src/part1/constants.py b/src/part1/constants.py
index 9abfbba2..974ccda9 100644
--- a/src/part1/constants.py
+++ b/src/part1/constants.py
@@ -19,20 +19,20 @@
 # Все константы, зависящие от ёмкостей *_BITS, должны вычисляться из них.
 
 # Twitter's original Snowflake epoch: 2010-11-04 01:42:54.657 UTC.
-EPOCH_MS_DEFAULT: Final[int] = 0
+EPOCH_MS_DEFAULT: Final[int] = 1288834974657
 
 # Node identifier used when the caller does not supply one.
-NODE_ID_DEFAULT: Final[int] = 0
+NODE_ID_DEFAULT: Final[int] = 1
 
 # Width of each field, in bits.
-TIMESTAMP_BITS: Final[int] = 0
-NODE_ID_BITS: Final[int] = 0
-SEQUENCE_ID_BITS: Final[int] = 0
+TIMESTAMP_BITS: Final[int] = 41
+NODE_ID_BITS: Final[int] = 10
+SEQUENCE_ID_BITS: Final[int] = 12
 
 # Largest value each field can hold.
-TIMESTAMP_MS_MAX: Final[int] = 0
-NODE_ID_MAX: Final[int] = 0
-SEQUENCE_ID_MAX: Final[int] = 0
+TIMESTAMP_MS_MAX: Final[int] = (1 << TIMESTAMP_BITS) - 1
+NODE_ID_MAX: Final[int] = (1 << NODE_ID_BITS) - 1
+SEQUENCE_ID_MAX: Final[int] = (1 << SEQUENCE_ID_BITS) - 1
 
 # Здесь можно добавить собственные вспомогательные константы
 # (например, сдвиги полей при сборке идентификатора).
diff --git a/src/part1/snowflake.py b/src/part1/snowflake.py
index d3abf050..d2a87fb8 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -13,73 +13,39 @@
 :func:`decode_node_id` and :func:`decode_sequence_id`.
 """
 
-import time  # noqa: F401
+import time
 
-from .constants import (  # noqa: F401
+from .constants import (
     EPOCH_MS_DEFAULT,
+    NODE_ID_BITS,
     NODE_ID_DEFAULT,
     NODE_ID_MAX,
+    SEQUENCE_ID_BITS,
     SEQUENCE_ID_MAX,
     TIMESTAMP_MS_MAX,
 )
 
 
 def read_current_millis(epoch_ms: int) -> int:
-    """Read the number of milliseconds elapsed since the custom epoch.
-
-    Args:
-        epoch_ms: The custom epoch expressed as Unix milliseconds.
-
-    Returns:
-        The count of whole milliseconds between ``epoch_ms`` and now. May be
-        negative if ``epoch_ms`` lies in the future.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    current_time_ms = int(time.time() * 1000)
+    timestamp_ms = current_time_ms - epoch_ms
+    return timestamp_ms
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
-    """Read the timestamp field out of a Snowflake identifier.
-
-    Args:
-        snowflake_id: An identifier produced against the same epoch.
-        epoch_ms: The epoch the identifier was generated against. Defaults to
-            the original Twitter epoch (2010-11-04 01:42:54.657 UTC).
-
-    Returns:
-        The absolute Unix time in milliseconds at which the identifier was
-        generated.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    timestamp_ms = snowflake_id >> (SEQUENCE_ID_BITS + NODE_ID_BITS)
+    current_time_ms = timestamp_ms + epoch_ms
+    return current_time_ms
 
 
 def decode_node_id(snowflake_id: int) -> int:
-    """Read the node identifier field out of a Snowflake identifier.
-
-    Args:
-        snowflake_id: An identifier produced by :func:`generate_snowflake_id`.
-
-    Returns:
-        The node identifier packed into ``snowflake_id``, in the range
-        ``[0, NODE_ID_MAX]``.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    node_id = (snowflake_id & (NODE_ID_MAX << SEQUENCE_ID_BITS)) >> SEQUENCE_ID_BITS
+    return node_id
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
-    """Read the sequence counter field out of a Snowflake identifier.
-
-    Args:
-        snowflake_id: An identifier produced by :func:`generate_snowflake_id`.
-
-    Returns:
-        The per-millisecond sequence counter packed into ``snowflake_id``, in
-        the range ``[0, SEQUENCE_ID_MAX]``.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    sequence_id = snowflake_id & (SEQUENCE_ID_MAX)
+    return sequence_id
 
 
 def generate_snowflake_id(
@@ -87,28 +53,17 @@ def generate_snowflake_id(
     node_id: int = NODE_ID_DEFAULT,
     epoch_ms: int = EPOCH_MS_DEFAULT,
 ) -> int | None:
-    """Build and return a Snowflake identifier for the current millisecond.
-
-    The function is stateless: the caller passes the per-millisecond sequence
-    counter explicitly. It is the caller's responsibility to increment
-    ``sequence_id`` for identifiers minted within the same millisecond and to
-    reset it once the clock advances.
-
-    Args:
-        sequence_id: The per-millisecond sequence counter, in the range
-            ``[0, SEQUENCE_ID_MAX]``.
-        node_id: The identifier of this node, in the range ``[0, NODE_ID_MAX]``.
-            Optional; defaults to ``NODE_ID_DEFAULT``.
-        epoch_ms: The start of the epoch as Unix milliseconds. Optional;
-            defaults to the original Twitter epoch (2010-11-04 01:42:54.657
-            UTC).
-
-    Returns:
-        The Snowflake identifier as a positive 63-bit integer, or ``None`` if
-        ``node_id`` is outside ``[0, NODE_ID_MAX]``, ``sequence_id`` is outside
-        ``[0, SEQUENCE_ID_MAX]``, or the elapsed time no longer fits in the
-        timestamp field (roughly 69 years after ``epoch_ms``). In each of those
-        cases an explanatory message is printed to stdout first.
-    """
-    # TODO: реализуйте функцию
-    return 0
+
+    if not (0 <= node_id <= NODE_ID_MAX):
+        return print(f"node_id ({node_id}) must be in [0, {NODE_ID_MAX}]")
+    if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
+        return print(f"sequence_id ({sequence_id}) must be in [0, {SEQUENCE_ID_MAX}]")
+    timestamp_ms = read_current_millis(epoch_ms)
+    if timestamp_ms > TIMESTAMP_MS_MAX:
+        return print("overflows")
+
+    timestamp_ms_snowflake_id = timestamp_ms << (SEQUENCE_ID_BITS + NODE_ID_BITS)
+    node_snowflake_id = node_id << SEQUENCE_ID_BITS
+    sequence_snowflake_id = sequence_id
+    snowflake_id = timestamp_ms_snowflake_id + node_snowflake_id + sequence_snowflake_id
+    return snowflake_id
diff --git a/src/part2/cart.py b/src/part2/cart.py
index 063f9aea..d0dc094d 100644
--- a/src/part2/cart.py
+++ b/src/part2/cart.py
@@ -22,9 +22,18 @@
 
 type CartLine = tuple[int, int]
 
-# TODO: задайте позиции полей внутри кортежа CartLine
 LINE_PRODUCT_ID_INDEX: Final = 0
-LINE_QUANTITY_INDEX: Final = 0
+LINE_QUANTITY_INDEX: Final = 1
+
+
+def find_cart_line(
+    cart: list[CartLine],
+    product_id: int,
+) -> CartLine | None:
+    for line in cart:
+        if line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return line
+    return None
 
 
 def add_to_cart(
@@ -33,28 +42,24 @@ def add_to_cart(
     product_id: int,
     quantity: int,
 ) -> CartLine | None:
-    """Move ``quantity`` units of ``product_id`` from the store into ``cart``.
-
-    The product is looked up in ``storage``. If it is missing, a message is
-    printed (by :func:`~src.part2.crud.read_product`) and nothing
-    changes. If the store holds fewer units than requested, an explanatory
-    message is printed and nothing changes. Otherwise the store record is
-    decremented by ``quantity`` and the cart line for ``product_id`` gains
-    ``quantity`` units -- a new line is created when the cart had none.
-
-    Args:
-        storage: The product store to draw stock from; modified in place on
-            success.
-        cart: The cart to add the units to; modified in place on success.
-        product_id: The identifier of the product to add.
-        quantity: Number of units to move into the cart.
-
-    Returns:
-        The cart line for ``product_id`` after the addition, or ``None``
-        when the product is unknown or the store cannot cover the request.
-    """
-    # TODO: реализуйте функцию
-    return (0, 0)
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+    if product[QUANTITY_INDEX] < quantity:
+        return print(
+            f"not enough stock for product {product_id}: {product[QUANTITY_INDEX]} available, {quantity} requested"
+        )
+    id, name, price, stock_quantity = product
+    updated_product = (id, name, price, stock_quantity - quantity)
+    storage[storage.index(product)] = updated_product
+    for line in cart:
+        if line[LINE_PRODUCT_ID_INDEX] == product_id:
+            updated_line = (product_id, line[LINE_QUANTITY_INDEX] + quantity)
+            cart[cart.index(line)] = updated_line
+            return updated_line
+    new_line = (product_id, quantity)
+    cart.append(new_line)
+    return new_line
 
 
 def remove_from_cart(
@@ -63,27 +68,23 @@ def remove_from_cart(
     product_id: int,
     quantity: int,
 ) -> CartLine | None:
-    """Move ``quantity`` units of ``product_id`` from ``cart`` back to the store.
-
-    The cart line for ``product_id`` is looked up. If there is none, a
-    message is printed and nothing changes. If the line holds fewer units
-    than requested, an explanatory message is printed and nothing changes.
-    Otherwise the cart line loses ``quantity`` units -- the line is dropped
-    when it reaches zero -- and the store record gains ``quantity`` units
-    back.
-
-    Args:
-        storage: The product store to return stock to; modified in place on
-            success.
-        cart: The cart to take the units from; modified in place on
-            success.
-        product_id: The identifier of the product to remove.
-        quantity: Number of units to move back into the store.
-
-    Returns:
-        The cart line for ``product_id`` after the removal (a quantity of
-        zero means the line was dropped), or ``None`` when the cart has no
-        line for the product or holds too few units.
-    """
-    # TODO: реализуйте функцию
-    return (0, 0)
+    line = find_cart_line(cart, product_id)
+    if line == None:
+        return print(f"product {product_id} is not in the cart")
+    if line[LINE_QUANTITY_INDEX] < quantity:
+        return print(
+            f"cart holds only {line[LINE_QUANTITY_INDEX]} unit(s) of product {product_id}, cannot remove {quantity}"
+        )
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+    id, name, price, storage_quantity = product
+    updated_product = (id, name, price, storage_quantity + quantity)
+    storage[storage.index(product)] = updated_product
+    id, cart_quantity = line
+    updated_line = (id, cart_quantity - quantity)
+    if cart_quantity - quantity == 0:
+        cart.remove(line)
+    else:
+        cart[cart.index(line)] = updated_line
+    return updated_line
diff --git a/src/part2/crud.py b/src/part2/crud.py
index d026cbcb..b7ec22be 100644
--- a/src/part2/crud.py
+++ b/src/part2/crud.py
@@ -14,66 +14,39 @@
 
 from decimal import Decimal
 
-from .storage import (  # noqa: F401
+from .storage import (
     NAME_INDEX,
     PRODUCT_ID_INDEX,
     PRODUCT_ID_MIN,
     Product,
 )
-from .utils import normalize_price  # noqa: F401
+from .utils import normalize_price
 
 
 def generate_product_id(storage: list[Product]) -> int:
-    """Choose the identifier for the next product added to ``storage``.
-
-    Args:
-        storage: The product store to inspect.
-
-    Returns:
-        One past the greatest identifier currently held in ``storage``, or
-        :data:`~src.part2.storage.PRODUCT_ID_MIN` when ``storage`` is
-        empty.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    if len(storage) == 0:
+        return PRODUCT_ID_MIN
+    return max(product[PRODUCT_ID_INDEX] for product in storage) + 1
 
 
 def create_product(
     storage: list[Product], fields: tuple[str, Decimal, int]
 ) -> int | None:
-    """Append a new product to ``storage`` and return its new identifier.
-
-    Args:
-        storage: The product store to append to; modified in place on
-            success.
-        fields: A ``(name, price, quantity)`` tuple describing the product.
-            ``price`` is a :class:`~decimal.Decimal` amount and is rounded
-            to the stored money precision before it is saved.
-
-    Returns:
-        The identifier generated for the new product, or ``None`` when a
-        product with the same name already exists. In the ``None`` case
-        ``storage`` is left unchanged and a message naming the clashing
-        name is printed.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    name, price, quantity = fields
+    if name in [product[NAME_INDEX] for product in storage]:
+        return print(f"product name {name} is already taken")
+    new_id = generate_product_id(storage)
+    price = normalize_price(price)
+    product = (new_id, name, price, quantity)
+    storage.append(product)
+    return new_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
-    """Return the product stored under ``product_id``.
-
-    Args:
-        storage: The product store to search.
-        product_id: The identifier to look up.
-
-    Returns:
-        The matching ``(product_id, name, price, quantity)`` record, or
-        ``None`` when no product carries that identifier (a message is
-        printed in that case).
-    """
-    # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            return product
+    return print(f"no product with id {product_id}")
 
 
 def update_product(
@@ -81,40 +54,19 @@ def update_product(
     product_id: int,
     fields: tuple[str, Decimal, int],
 ) -> Product | None:
-    """Overwrite the fields of the product stored under ``product_id``.
-
-    The identifier itself is preserved; only ``name``, ``price`` and
-    ``quantity`` are replaced.
-
-    Args:
-        storage: The product store to modify; the matching record is
-            replaced in place on success.
-        product_id: The identifier of the product to change.
-        fields: A ``(name, price, quantity)`` tuple with the new values.
-            ``price`` is a :class:`~decimal.Decimal` amount and is rounded
-            to the stored money precision before it is saved.
-
-    Returns:
-        The updated ``(product_id, name, price, quantity)`` record, or
-        ``None`` when no product carries that identifier (``storage`` is
-        left unchanged and a message is printed).
-    """
-    # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            name, price, quantity = fields
+            price = normalize_price(price)
+            updated_product = (product_id, name, price, quantity)
+            storage[storage.index(product)] = updated_product
+            return updated_product
+    return print(f"no product with id {product_id}")
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
-    """Remove the product stored under ``product_id`` from ``storage``.
-
-    Args:
-        storage: The product store to remove from; modified in place on
-            success.
-        product_id: The identifier of the product to remove.
-
-    Returns:
-        ``product_id`` when a product was removed, or ``None`` when no
-        product carried that identifier (``storage`` is left unchanged and
-        a message is printed).
-    """
-    # TODO: реализуйте функцию
-    return 0
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            storage.remove(product)
+            return product_id
+    return print(f"no product with id {product_id}")
diff --git a/src/part2/storage.py b/src/part2/storage.py
index b63d5fc7..e4bceff1 100644
--- a/src/part2/storage.py
+++ b/src/part2/storage.py
@@ -24,11 +24,9 @@
 
 type Product = tuple[int, str, Decimal, int]
 
-# TODO: задайте позиции полей внутри кортежа Product
 PRODUCT_ID_INDEX: Final = 0
-NAME_INDEX: Final = 0
-PRICE_INDEX: Final = 0
-QUANTITY_INDEX: Final = 0
+NAME_INDEX: Final = 1
+PRICE_INDEX: Final = 2
+QUANTITY_INDEX: Final = 3
 
-# TODO: задайте идентификатор первого товара в пустом хранилище
-PRODUCT_ID_MIN: Final[int] = 0
+PRODUCT_ID_MIN: Final[int] = 1
diff --git a/src/part2/utils.py b/src/part2/utils.py
index 11bd7a76..413f9564 100644
--- a/src/part2/utils.py
+++ b/src/part2/utils.py
@@ -6,24 +6,13 @@
 currency values free of binary floating-point error.
 """
 
-from decimal import ROUND_HALF_UP, Decimal  # noqa: F401
+from decimal import ROUND_HALF_UP, Decimal
 from typing import Final
 
 
-# TODO: задайте число знаков после запятой и шаг квантования
-PRICE_PRECISION: Final[int] = 0
-PRICE_STEP: Final = Decimal(0)
+PRICE_PRECISION: Final[int] = 2
+PRICE_STEP: Final = Decimal(1).scaleb(-PRICE_PRECISION)
 
 
 def normalize_price(price: Decimal) -> Decimal:
-    """Round a price to the precision every stored record uses.
-
-    Args:
-        price: The raw price amount.
-
-    Returns:
-        ``price`` quantised to :data:`PRICE_PRECISION` fractional digits,
-        with halves rounded up.
-    """
-    # TODO: реализуйте функцию
-    return Decimal(0)
+    return price.quantize(PRICE_STEP, ROUND_HALF_UP)
diff --git a/src/part3/crud.py b/src/part3/crud.py
index 68811d7e..2933816c 100644
--- a/src/part3/crud.py
+++ b/src/part3/crud.py
@@ -20,68 +20,42 @@
 
 from decimal import Decimal
 
-from .storage import (  # noqa: F401
+from .storage import (
     NAME_INDEX,
     PRODUCT_ID_INDEX,
     PRODUCT_ID_MIN,
     Product,
 )
-from .utils import normalize_price, normalize_product_name  # noqa: F401
+from .utils import normalize_price, normalize_product_name
 
 
 def generate_product_id(storage: list[Product]) -> int:
-    """Choose the identifier for the next product added to ``storage``.
-
-    Args:
-        storage: The product store to inspect.
-
-    Returns:
-        One past the greatest identifier currently held in ``storage``, or
-        :data:`~src.part3.storage.PRODUCT_ID_MIN` when ``storage`` is
-        empty.
-    """
-    # TODO: реализуйте функцию (используйте своё решение части 2)
-    return 0
+    if len(storage) == 0:
+        return PRODUCT_ID_MIN
+    return max(product[PRODUCT_ID_INDEX] for product in storage) + 1
 
 
 def create_product(
     storage: list[Product], fields: tuple[str, Decimal, int]
 ) -> int | None:
-    """Append a new product to ``storage`` and return its new identifier.
-
-    Args:
-        storage: The product store to append to; modified in place on
-            success.
-        fields: A ``(name, price, quantity)`` tuple describing the product.
-            ``name`` is normalised (surrounding whitespace stripped,
-            lower-cased) before it is stored or compared. ``price`` is a
-            :class:`~decimal.Decimal` amount and is rounded to the stored
-            money precision before it is saved.
-
-    Returns:
-        The identifier generated for the new product, or ``None`` when
-        ``name`` is blank once normalised or a product with the same
-        normalised name already exists. In the ``None`` case ``storage``
-        is left unchanged and an explanatory message is printed.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    name, price, quantity = fields
+    name = normalize_product_name(name)
+    if name == "":
+        return print("product name must not be blank")
+    if name in [product[NAME_INDEX] for product in storage]:
+        return print(f"product name '{name}' is already taken")
+    new_id = generate_product_id(storage)
+    price = normalize_price(price)
+    product = (new_id, name, price, quantity)
+    storage.append(product)
+    return new_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
-    """Return the product stored under ``product_id``.
-
-    Args:
-        storage: The product store to search.
-        product_id: The identifier to look up.
-
-    Returns:
-        The matching ``(product_id, name, price, quantity)`` record, or
-        ``None`` when no product carries that identifier (a message is
-        printed in that case).
-    """
-    # TODO: реализуйте функцию (используйте своё решение части 2)
-    return (0, "", Decimal(0), 0)
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            return product
+    return print(f"no product with id {product_id}")
 
 
 def update_product(
@@ -89,43 +63,33 @@ def update_product(
     product_id: int,
     fields: tuple[str, Decimal, int],
 ) -> Product | None:
-    """Overwrite the fields of the product stored under ``product_id``.
-
-    The identifier itself is preserved; only ``name``, ``price`` and
-    ``quantity`` are replaced.
-
-    Args:
-        storage: The product store to modify; the matching record is
-            replaced in place on success.
-        product_id: The identifier of the product to change.
-        fields: A ``(name, price, quantity)`` tuple with the new values.
-            ``price`` is a :class:`~decimal.Decimal` amount and is rounded
-            to the stored money precision before it is saved.
-
-    Returns:
-        The updated ``(product_id, name, price, quantity)`` record, or
-        ``None`` when ``name`` is blank once normalised, no product
-        carries that identifier, or the normalised name is already taken
-        by another product. In every ``None`` case ``storage`` is left
-        unchanged and an explanatory message is printed. Renaming a
-        product to its own current name is allowed.
-    """
-    # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+
+    name, price, quantity = fields
+    name = normalize_product_name(name)
+    if name == "":
+        return print("product name must not be blank")
+
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+
+    for other_product in storage:
+        if (
+            other_product[NAME_INDEX] == name
+            and other_product[PRODUCT_ID_INDEX] != product_id
+        ):
+            return print(f"product name '{name}' is already taken")
+
+    price = normalize_price(price)
+    updated_product = (product_id, name, price, quantity)
+    storage[storage.index(product)] = updated_product
+
+    return updated_product
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
-    """Remove the product stored under ``product_id`` from ``storage``.
-
-    Args:
-        storage: The product store to remove from; modified in place on
-            success.
-        product_id: The identifier of the product to remove.
-
-    Returns:
-        ``product_id`` when a product was removed, or ``None`` when no
-        product carried that identifier (``storage`` is left unchanged and
-        a message is printed).
-    """
-    # TODO: реализуйте функцию (используйте своё решение части 2)
-    return 0
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            storage.remove(product)
+            return product_id
+    return print(f"no product with id {product_id}")
diff --git a/src/part3/run_admin.py b/src/part3/run_admin.py
index c5feeb0b..d1f1a741 100644
--- a/src/part3/run_admin.py
+++ b/src/part3/run_admin.py
@@ -29,79 +29,84 @@
 it.
 """
 
-from decimal import Decimal, InvalidOperation  # noqa: F401
+from decimal import Decimal, InvalidOperation
 from typing import Final
 
-from .crud import (  # noqa: F401
+from .crud import (
     create_product,
     delete_product,
     read_product,
     update_product,
 )
 from .storage import Product
-from .utils import get_storage_str_representation  # noqa: F401
+from .utils import get_storage_str_representation
 
 
-# TODO: задайте приглашение и текст справки
-PROMPT: Final[str] = ""
-HELP_TEXT: Final[str] = ""
+PROMPT: Final[str] = "admin> "
+HELP_TEXT: Final[str] = """Available commands:
+  help                                       show this message
+  exit                                       leave the console
+  show                                       print the whole store as a table
+  create <name...> <price> <quantity>        add a product, print its new id
+  read <id>                                  print the product with that id
+  update <id> <name...> <price> <quantity>   overwrite that product's fields
+  delete <id>                                remove the product with that id
 
+For create and update the price and quantity are the last two words of the
+line; everything before them is the product name, so it may contain spaces
+(for example "Gibson SG Junior") and needs no quoting."""
 
-def show_help() -> None:
-    """Print the command reference to stdout.
 
-    The text is the module-level :data:`HELP_TEXT` constant, printed as
-    is: a heading, one line per command with a short description, and a
-    note on how multi-word names are parsed.
-    """
-    # TODO: реализуйте функцию
+def show_help() -> None:
+    print(HELP_TEXT)
 
 
 def print_result(result: object) -> None:
-    """Print a CRUD result to stdout unless it is ``None``.
-
-    Args:
-        result: The value returned by a CRUD operation. ``None`` means the
-            operation already reported its own failure, so nothing is
-            printed in that case.
-    """
-    # TODO: реализуйте функцию
+    if result is not None:
+        print(result)
 
 
 def run_command(storage: list[Product], line: str) -> bool:
-    """Parse one console line and carry out the command it names.
+    match line.split():
+        case ["help"]:
+            show_help()
+
+        case ["exit"]:
+            return False
 
-    Args:
-        storage: The product store shared across the session; mutated in
-            place by the ``create``, ``update`` and ``delete`` commands.
-        line: One line of console input, already stripped of surrounding
-            whitespace.
+        case ["show"]:
+            print(get_storage_str_representation(storage))
 
-    Returns:
-        ``True`` to keep the read-eval-print loop running, or ``False``
-        once the ``exit`` command has been seen. A line that is not a
-        known command prints a notice and still returns ``True``.
+        case ["read", product_id]:
+            print_result(read_product(storage, int(product_id)))
 
-    Raises:
-        ValueError: If an id or quantity argument of a CRUD command does
-            not parse as a base-10 integer.
-        decimal.InvalidOperation: If the price argument of ``create`` or
-            ``update`` does not parse as a decimal number.
-    """
-    # TODO: реализуйте функцию
-    return False
+        case ["delete", product_id]:
+            print_result(delete_product(storage, int(product_id)))
+
+        case ["create", *name_parts, price, quantity] if name_parts:
+            name = " ".join(name_parts)
+            price_decimal = Decimal(price)
+            quantity_int = int(quantity)
+            print_result(create_product(storage, (name, price_decimal, quantity_int)))
+
+        case ["update", product_id, *name_parts, price, quantity] if name_parts:
+            product_id_int = int(product_id)
+            name = " ".join(name_parts)
+            price_decimal = Decimal(price)
+            quantity_int = int(quantity)
+            print_result(
+                update_product(
+                    storage, product_id_int, (name, price_decimal, quantity_int)
+                )
+            )
+
+        case _:
+            print(f"'{line}' is not a command")
+    return True
 
 
 def main() -> None:
-    """Run the admin console until the ``exit`` command is entered.
-
-    A single product store is created empty and kept in memory for the
-    whole session. Each iteration reads one line from stdin, strips its
-    surrounding whitespace and hands it to :func:`run_command`. A line
-    that names a command but whose id, price or quantity argument does
-    not parse is caught here and reported without stopping the loop; only
-    ``exit`` ends it.
-    """
+
     storage: list[Product] = []
     running = True
 
diff --git a/src/part3/storage.py b/src/part3/storage.py
index c5e34be5..c516645b 100644
--- a/src/part3/storage.py
+++ b/src/part3/storage.py
@@ -24,12 +24,9 @@
 
 type Product = tuple[int, str, Decimal, int]
 
-# TODO: задайте позиции полей внутри кортежа Product (используйте своё решение
-# части 2)
 PRODUCT_ID_INDEX: Final = 0
-NAME_INDEX: Final = 0
-PRICE_INDEX: Final = 0
-QUANTITY_INDEX: Final = 0
+NAME_INDEX: Final = 1
+PRICE_INDEX: Final = 2
+QUANTITY_INDEX: Final = 3
 
-# TODO: задайте идентификатор первого товара в пустом хранилище
-PRODUCT_ID_MIN: Final[int] = 0
+PRODUCT_ID_MIN: Final[int] = 1
diff --git a/src/part3/tests/TESTS.md b/src/part3/tests/TESTS.md
new file mode 100644
index 00000000..93dfe8dd
--- /dev/null
+++ b/src/part3/tests/TESTS.md
@@ -0,0 +1,62 @@
+# Тесты Part 3
+
+## Описание тестов
+
+### Базовые функции
+- **test_normalize_product_name** — нормализация имён товаров (приведение к нижнему регистру, удаление лишних пробелов)
+- **test_constants** — проверка значений констант (промпт и заголовки таблицы)
+
+### Представление данных
+- **test_get_storage_str_representation** — форматирование хранилища в таблицу (проверка выравнивания, разделители, инварианты)
+
+### CRUD операции
+- **test_create_product** — создание товара: валидация имён, проверка дубликатов, генерация ID
+- **test_update_product** — обновление товара: валидация, проверка конфликтов имён, обработка отсутствующих ID
+
+### Команды
+- **test_run_command_help_exit** — команды help и exit
+- **test_run_command_create** — команда create (нормализация имени, округление цены)
+- **test_run_command_show** — команда show (вывод таблицы)
+- **test_run_command_read** — команда read (чтение товара по ID)
+- **test_run_command_update** — команда update (обновление товара)
+- **test_run_command_delete** — команда delete (удаление товара)
+- **test_run_command_not_a_command** — обработка неверных команд и аргументов
+- **test_run_command_invalid_arguments** — парсинг некорректных значений (ID, цена, количество)
+
+### Интеграционные тесты
+- **test_show_help** — вывод справки
+- **test_print_result** — форматирование результатов команд
+- **test_main_session** — полный сеанс работы администратора
+- **test_main_catches_invalid_arguments** — обработка ошибок парсинга в main
+
+## Запуск
+
+### Windows
+```cmd
+# Из корня проекта
+python -m pytest src/part3/tests/test_general.py -v
+
+# Или конкретный тест
+python -m pytest src/part3/tests/test_general.py::test_normalize_product_name -v
+```
+
+### macOS / Linux (Ubuntu, Fedora)
+```bash
+# Из корня проекта
+python -m pytest src/part3/tests/test_general.py -v
+
+# Или конкретный тест
+python -m pytest src/part3/tests/test_general.py::test_normalize_product_name -v
+
+# С покрытием кода
+python -m pytest src/part3/tests/test_general.py --cov=src/part3 --cov-report=term-missing
+```
+
+### Без запуска всех
+```bash
+# Только быстрые тесты
+python -m pytest src/part3/tests/test_general.py -v -k "not main"
+
+# Прерваться на первой ошибке
+python -m pytest src/part3/tests/test_general.py -x
+```
diff --git a/src/part3/tests/__init__.py b/src/part3/tests/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/src/part3/tests/test_general.py b/src/part3/tests/test_general.py
new file mode 100644
index 00000000..9e9a30e2
--- /dev/null
+++ b/src/part3/tests/test_general.py
@@ -0,0 +1,377 @@
+from decimal import Decimal, InvalidOperation
+
+import pytest
+
+from ..crud import create_product, update_product
+from ..run_admin import HELP_TEXT, PROMPT, main, print_result, run_command, show_help
+from ..storage import Product
+from ..utils import (
+    TABLE_HEADERS,
+    get_storage_str_representation,
+    normalize_product_name,
+)
+
+
+def test_normalize_product_name() -> None:
+    assert normalize_product_name("  Cordless Drill  ") == "cordless drill"
+    assert normalize_product_name("abc    def\tghi\tjkl") == "abc def ghi jkl"
+    assert normalize_product_name(" \t\n ") == ""
+    assert normalize_product_name("claw hammer") == "claw hammer"
+    assert normalize_product_name("") == ""
+    assert normalize_product_name("Cordless\tDrill\n  ") == "cordless drill"
+
+
+def test_constants() -> None:
+    assert PROMPT == "admin> "
+    assert TABLE_HEADERS == ("ID", "name", "price", "quantity")
+
+
+def test_get_storage_str_representation() -> None:
+    # пустое хранилище: только заголовки и разделитель
+    assert (
+        get_storage_str_representation([])
+        == """| ID | name | price | quantity |
+|----|------|-------|----------|"""
+    )
+
+    test1_str = """| ID | name | price | quantity |
+|----|------|-------|----------|
+| 1  | saw  | 9.90  | 5        |
+| 2  | axe  | 12.00 | 8        |"""
+    assert (
+        get_storage_str_representation(
+            [(1, "saw", Decimal("9.90"), 5), (2, "axe", Decimal("12.00"), 8)]
+        )
+        == test1_str
+    )
+
+    test2_str = """| ID | name       | price   | quantity |
+|----|------------|---------|----------|
+| 10 | compressor | 1299.99 | 3        |
+| 2  | nail       | 2.50    | 500      |"""
+    assert (
+        get_storage_str_representation(
+            [
+                (10, "compressor", Decimal("1299.99"), 3),
+                (2, "nail", Decimal("2.50"), 500),
+            ]
+        )
+        == test2_str
+    )
+
+    # инварианты: все строки одной длины, | на краях каждой строки
+    lines = test2_str.split("\n")
+    assert len({len(line) for line in lines}) == 1
+    assert all(line.startswith("|") and line.endswith("|") for line in lines)
+
+
+def test_create_product(capsys: pytest.CaptureFixture[str]) -> None:
+    taken: list[Product] = [
+        (1, "saw", Decimal("9.90"), 5),
+        (2, "axe", Decimal("12.00"), 8),
+    ]
+
+    # пустое имя: пустая строка или только пробельные символы
+    for name in ("", "   ", " \n \t "):
+        assert create_product(taken, (name, Decimal("1.00"), 1)) is None
+        assert capsys.readouterr().out == "product name must not be blank\n"
+
+    # имя занято, сравнение идёт по нормализованной форме
+    assert create_product(taken, ("saw", Decimal("1.00"), 1)) is None
+    assert capsys.readouterr().out == "product name 'saw' is already taken\n"
+    assert create_product(taken, (" SAw   ", Decimal("1.00"), 1)) is None
+    assert capsys.readouterr().out == "product name 'saw' is already taken\n"
+    assert taken == [
+        (1, "saw", Decimal("9.90"), 5),
+        (2, "axe", Decimal("12.00"), 8),
+    ]
+
+    # успех: имя и цена нормализуются, id на один больше наибольшего
+    assert create_product(taken, ("sword", Decimal("1.00"), 1)) == 3
+    assert taken == [
+        (1, "saw", Decimal("9.90"), 5),
+        (2, "axe", Decimal("12.00"), 8),
+        (3, "sword", Decimal("1.00"), 1),
+    ]
+
+    # id считается как max + 1, а не len + 1
+    gappy: list[Product] = [
+        (1, "saw", Decimal("9.90"), 5),
+        (3, "axe", Decimal("12.00"), 8),
+    ]
+    assert create_product(gappy, ("sword", Decimal("1.00"), 1)) == 4
+
+    # примеры из TASK.md
+    storage1: list[Product] = []
+    first_id = create_product(storage1, ("  Cordless   Drill ", Decimal("89.999"), 12))
+    second_id = create_product(storage1, ("Claw Hammer", Decimal("9.9"), 40))
+    assert first_id == 1
+    assert second_id == 2
+    assert storage1 == [
+        (1, "cordless drill", Decimal("90.00"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+    storage2: list[Product] = []
+    assert create_product(storage2, ("cordless drill", Decimal(50), 3)) == 1
+    result = create_product(storage2, ("  CORDLESS   DRILL  ", Decimal(75), 1))
+    assert result is None
+    assert capsys.readouterr().out == "product name 'cordless drill' is already taken\n"
+    assert storage2 == [(1, "cordless drill", Decimal("50.00"), 3)]
+
+    storage3: list[Product] = []
+    result = create_product(storage3, ("     ", Decimal(10), 5))
+    assert result is None
+    assert capsys.readouterr().out == "product name must not be blank\n"
+    assert storage3 == []
+
+
+def test_update_product(capsys: pytest.CaptureFixture[str]) -> None:
+    storage1: list[Product] = [
+        (1, "cordless drill", Decimal("90.00"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+    # успех: имя и цена нормализуются, идентификатор сохраняется
+    result = update_product(storage1, 2, ("  Rubber   Mallet ", Decimal("7.505"), 25))
+    assert result == (2, "rubber mallet", Decimal("7.51"), 25)
+    assert storage1 == [
+        (1, "cordless drill", Decimal("90.00"), 12),
+        (2, "rubber mallet", Decimal("7.51"), 25),
+    ]
+
+    storage2: list[Product] = [
+        (1, "cordless drill", Decimal("90.00"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+    # обновление под собственным именем (в другом написании) — не конфликт
+    result = update_product(storage2, 1, ("CORDLESS  Drill", Decimal(85), 10))
+    assert result == (1, "cordless drill", Decimal("85.00"), 10)
+
+    storage3: list[Product] = [
+        (1, "cordless drill", Decimal("90.00"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+    # имя занято другим товаром
+    result = update_product(storage3, 1, (" Claw Hammer ", Decimal(85), 10))
+    assert result is None
+    assert capsys.readouterr().out == "product name 'claw hammer' is already taken\n"
+    assert storage3 == [
+        (1, "cordless drill", Decimal("90.00"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+    storage4: list[Product] = [
+        (1, "cordless drill", Decimal("90.00"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+    # товара с таким id нет
+    result = update_product(storage4, 99, ("saw", Decimal(20), 5))
+    assert result is None
+    assert capsys.readouterr().out == "no product with id 99\n"
+
+    # пустое имя отвергается до поиска по идентификатору
+    result = update_product(storage4, 99, ("     ", Decimal(20), 5))
+    assert result is None
+    assert capsys.readouterr().out == "product name must not be blank\n"
+    assert storage4 == [
+        (1, "cordless drill", Decimal("90.00"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+
+def test_show_help(capsys: pytest.CaptureFixture[str]) -> None:
+    show_help()
+    assert capsys.readouterr().out == HELP_TEXT + "\n"
+
+
+def test_print_result(capsys: pytest.CaptureFixture[str]) -> None:
+    print_result(None)
+    assert capsys.readouterr().out == ""
+
+    print_result(42)
+    assert capsys.readouterr().out == "42\n"
+
+    product: Product = (1, "saw", Decimal("9.90"), 5)
+    print_result(product)
+    assert capsys.readouterr().out == "(1, 'saw', Decimal('9.90'), 5)\n"
+
+
+def sample_storage() -> list[Product]:
+    """A fresh store with two products, for the run_command tests."""
+    return [
+        (1, "cordless drill", Decimal("89.99"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+
+def test_run_command_help_exit(capsys: pytest.CaptureFixture[str]) -> None:
+    storage: list[Product] = []
+
+    assert run_command(storage, "help") is True
+    assert capsys.readouterr().out == HELP_TEXT + "\n"
+
+    assert run_command(storage, "exit") is False
+    assert capsys.readouterr().out == ""
+    assert storage == []
+
+
+def test_run_command_create(capsys: pytest.CaptureFixture[str]) -> None:
+    storage: list[Product] = []
+
+    # имя нормализуется, цена округляется, печатается новый id
+    assert run_command(storage, "create Cordless Drill 89.99 12") is True
+    assert capsys.readouterr().out == "1\n"
+
+    assert run_command(storage, "create  claw   hammer 9.9 40") is True
+    assert capsys.readouterr().out == "2\n"
+    assert storage == [
+        (1, "cordless drill", Decimal("89.99"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+
+def test_run_command_show(capsys: pytest.CaptureFixture[str]) -> None:
+    storage: list[Product] = []
+
+    assert run_command(storage, "show") is True
+    assert capsys.readouterr().out == (
+        "| ID | name | price | quantity |\n|----|------|-------|----------|\n"
+    )
+
+    run_command(storage, "create Cordless Drill 89.99 12")
+    run_command(storage, "create  claw   hammer 9.9 40")
+    capsys.readouterr()
+
+    assert run_command(storage, "show") is True
+    assert capsys.readouterr().out == (
+        "| ID | name           | price | quantity |\n"
+        "|----|----------------|-------|----------|\n"
+        "| 1  | cordless drill | 89.99 | 12       |\n"
+        "| 2  | claw hammer    | 9.90  | 40       |\n"
+    )
+
+
+def test_run_command_read(capsys: pytest.CaptureFixture[str]) -> None:
+    storage = sample_storage()
+
+    assert run_command(storage, "read 1") is True
+    assert capsys.readouterr().out == "(1, 'cordless drill', Decimal('89.99'), 12)\n"
+
+    assert run_command(storage, "read 5") is True
+    assert capsys.readouterr().out == "no product with id 5\n"
+    assert storage == [
+        (1, "cordless drill", Decimal("89.99"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+
+def test_run_command_update(capsys: pytest.CaptureFixture[str]) -> None:
+    storage = sample_storage()
+
+    assert run_command(storage, "update 2 mallet 7.50 30") is True
+    assert capsys.readouterr().out == "(2, 'mallet', Decimal('7.50'), 30)\n"
+    assert storage == [
+        (1, "cordless drill", Decimal("89.99"), 12),
+        (2, "mallet", Decimal("7.50"), 30),
+    ]
+
+
+def test_run_command_delete(capsys: pytest.CaptureFixture[str]) -> None:
+    storage = sample_storage()
+
+    assert run_command(storage, "delete 2") is True
+    assert capsys.readouterr().out == "2\n"
+
+    assert run_command(storage, "delete 2") is True
+    assert capsys.readouterr().out == "no product with id 2\n"
+    assert storage == [(1, "cordless drill", Decimal("89.99"), 12)]
+
+
+def test_run_command_not_a_command(capsys: pytest.CaptureFixture[str]) -> None:
+    storage = sample_storage()
+
+    # неизвестная команда, неверное число аргументов и create/update без
+    # слов имени: одно и то же сообщение, хранилище не меняется
+    for line in (
+        "frobnicate 1 2",
+        "read 1 2 3",
+        "read",
+        "delete",
+        "help me",
+        "exit now",
+        "show extra",
+        "create 89.90 12",
+        "update 1 89.90 12",
+    ):
+        assert run_command(storage, line) is True
+        assert capsys.readouterr().out == f"'{line}' is not a command\n"
+    assert storage == [
+        (1, "cordless drill", Decimal("89.99"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+
+# помогла написать нейронка
+def test_run_command_invalid_arguments(capsys: pytest.CaptureFixture[str]) -> None:
+    storage = sample_storage()
+
+    # id/цена/количество не разбираются: исключение (ловится в main),
+    # хранилище и stdout не меняются
+    for line, exc_type in (
+        ("read abc", ValueError),
+        ("delete abc", ValueError),
+        ("update abc claw hammer 1.00 1", ValueError),
+        ("create foo 1.00 abc", ValueError),
+        ("create foo abc 5", InvalidOperation),
+        ("update 1 foo abc 2", InvalidOperation),
+    ):
+        with pytest.raises(exc_type):
+            run_command(storage, line)
+        assert capsys.readouterr().out == ""
+    assert storage == [
+        (1, "cordless drill", Decimal("89.99"), 12),
+        (2, "claw hammer", Decimal("9.90"), 40),
+    ]
+
+
+# помогла написать нейронка
+def test_main_session(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
+    lines = iter(
+        [
+            "create Cordless Drill 89.99 12",
+            "create  claw   hammer 9.9 40",
+            "show",
+            "read 5",
+            "exit",
+        ]
+    )
+    monkeypatch.setattr("builtins.input", lambda prompt="": next(lines))
+    main()
+    assert capsys.readouterr().out == (
+        "1\n"
+        "2\n"
+        "| ID | name           | price | quantity |\n"
+        "|----|----------------|-------|----------|\n"
+        "| 1  | cordless drill | 89.99 | 12       |\n"
+        "| 2  | claw hammer    | 9.90  | 40       |\n"
+        "no product with id 5\n"
+    )
+
+
+# Взял погонять у товарища
+def test_main_catches_invalid_arguments(
+    monkeypatch: pytest.MonkeyPatch, capsys: pytest.CaptureFixture[str]
+) -> None:
+    lines = iter(["create foo abc 5", "read x", "exit"])
+    monkeypatch.setattr("builtins.input", lambda prompt="": next(lines))
+    main()
+    assert capsys.readouterr().out == (
+        "'create foo abc 5' names a command but its arguments are invalid\n"
+        "'read x' names a command but its arguments are invalid\n"
+    )
diff --git a/src/part3/utils.py b/src/part3/utils.py
index 318ded0b..7073828d 100644
--- a/src/part3/utils.py
+++ b/src/part3/utils.py
@@ -18,78 +18,57 @@
   the longest value it holds in that particular call.
 """
 
-from decimal import ROUND_HALF_UP, Decimal  # noqa: F401
+from decimal import ROUND_HALF_UP, Decimal
 from typing import Final
 
 from .storage import Product
 
 
-# Number of fractional digits every stored price is rounded to.
-# Quantisation step derived from PRICE_PRECISION, e.g. Decimal("0.01").
-# TODO: задайте число знаков после запятой и шаг квантования (используйте своё
-# решение части 2)
-PRICE_PRECISION: Final[int] = 0
-PRICE_STEP: Final = Decimal(0)
+PRICE_PRECISION: Final[int] = 2
+PRICE_STEP: Final = Decimal(1).scaleb(-PRICE_PRECISION)
 
 # Column headers of the table produced by get_storage_str_representation,
 # left to right. The width of each column is not fixed here -- it is
 # measured per call from the data (see the function).
-# TODO: задайте заголовки столбцов таблицы
-TABLE_HEADERS: Final[tuple[str, ...]] = ()
+TABLE_HEADERS: Final[tuple[str, ...]] = ("ID", "name", "price", "quantity")
 
+storage: list[tuple[int, str, Decimal, int]] = []
 
-def normalize_price(price: Decimal) -> Decimal:
-    """Round a price to the precision every stored record uses.
-
-    Args:
-        price: The raw price amount.
 
-    Returns:
-        ``price`` quantised to :data:`PRICE_PRECISION` fractional digits,
-        with halves rounded up.
-    """
-    # TODO: реализуйте функцию (используйте своё решение части 2)
-    return Decimal(0)
+def normalize_price(price: Decimal) -> Decimal:
+    return price.quantize(PRICE_STEP, ROUND_HALF_UP)
 
 
 def normalize_product_name(name: str) -> str:
-    """Reduce a product name to the canonical form the store keeps.
-
-    Args:
-        name: The raw product name.
-
-    Returns:
-        ``name`` with every leading and trailing whitespace character
-        removed, every internal run of whitespace (spaces, tabs and the
-        like) collapsed to a single space, and the rest lower-cased. For
-        example ``"abc    def\tghi\tjkl"`` becomes ``"abc def ghi jkl"``.
-        The result is an empty string when ``name`` holds nothing but
-        whitespace.
-    """
-    # TODO: реализуйте функцию
-    return ""
-
-
-# TODO: при необходимости добавьте свои вспомогательные функции
+    return " ".join(name.split()).lower()
 
 
 def get_storage_str_representation(storage: list[Product]) -> str:
-    """Render the product store as a text table with data-sized columns.
-
-    The table has the columns named by :data:`TABLE_HEADERS` -- id, name,
-    price and quantity. Each column is made exactly as wide as the longest
-    value it carries in this call (its header counted), so the columns
-    line up when the string is printed to a terminal and no value is ever
-    truncated.
-
-    Args:
-        storage: The product store to render.
-
-    Returns:
-        A multi-line string: a header row, a dashed separator row, then
-        one row per product in ``storage`` in list order. When ``storage``
-        is empty only the header and separator rows are returned, sized to
-        the header labels.
-    """
-    # TODO: реализуйте функцию
-    return ""
+    column_width = [len(header) for header in TABLE_HEADERS]
+    for product in storage:
+        for i, value in enumerate(product):
+            column_width[i] = max(column_width[i], len(str(value)))
+    header_row = (
+        "|"
+        + "|".join(
+            f" {header.ljust(width)} "
+            for header, width in zip(TABLE_HEADERS, column_width)
+        )
+        + "|"
+    )
+    delimiter_row = "|" + "|".join("-" * (width + 2) for width in column_width) + "|"
+
+    table_rows = [header_row, delimiter_row]
+
+    for product in storage:
+        row = (
+            "|"
+            + "|".join(
+                f" {str(value).ljust(width)} "
+                for value, width in zip(product, column_width)
+            )
+            + "|"
+        )
+        table_rows.append(row)
+
+    return "\n".join(table_rows)
diff --git a/src/part4/cart.py b/src/part4/cart.py
index aed9bb72..fc4b0bfc 100644
--- a/src/part4/cart.py
+++ b/src/part4/cart.py
@@ -9,7 +9,7 @@
 an explanatory message to stdout and returns ``None``.
 """
 
-from .storage import Product
+from .storage import QUANTITY_KEY, Product
 
 
 # TODO: при необходимости добавьте свои вспомогательные функции
@@ -46,8 +46,20 @@ def add_to_cart(
         ``None`` when the product is unknown or the store cannot cover the
         request.
     """
-    # TODO: реализуйте функцию
-    return 0
+
+    if not (product := storage.get(product_id)):
+        return print(f"no product with id {product_id}")
+
+    if product[QUANTITY_KEY] < quantity:
+        return print(
+            f"not enough stock for product {product_id}: "
+            f"{product[QUANTITY_KEY]} available, {quantity} requested"
+        )
+
+    product[QUANTITY_KEY] -= quantity
+
+    cart[product_id] = cart.get(product_id, 0) + quantity
+    return cart[product_id]
 
 
 def remove_from_cart(
@@ -83,5 +95,23 @@ def remove_from_cart(
         (zero means the product was dropped from the cart), or ``None`` when
         the cart does not hold the product or holds too few units.
     """
-    # TODO: реализуйте функцию
-    return 0
+
+    if product_id not in cart:
+        return print(f"product {product_id} is not in cart")
+
+    if cart[product_id] < quantity:
+        return print(
+            f"cart holds only {cart[product_id]}"
+            f" units of product {product_id}, cannot remove {quantity}"
+        )
+
+    if not (product := storage.get(product_id)):
+        return print(f"no product with id {product_id}")
+
+    product[QUANTITY_KEY] += quantity
+
+    cart[product_id] -= quantity
+    if cart[product_id] == 0:
+        del cart[product_id]
+        return 0
+    return cart[product_id]
diff --git a/src/part4/crud.py b/src/part4/crud.py
index 471eff00..8c7a271e 100644
--- a/src/part4/crud.py
+++ b/src/part4/crud.py
@@ -23,16 +23,16 @@
 than a scan over ``storage.values()``.
 """
 
-import uuid  # noqa: F401
+import uuid
 from typing import Any
 
-from .storage import (  # noqa: F401
+from .storage import (
     NAME_KEY,
     PRICE_KEY,
     QUANTITY_KEY,
     Product,
 )
-from .utils import normalize_price, normalize_product_name  # noqa: F401
+from .utils import normalize_price, normalize_product_name
 
 
 def generate_product_id() -> str:
@@ -41,8 +41,8 @@ def generate_product_id() -> str:
     Returns:
         A freshly generated UUID, stringified.
     """
-    # TODO: реализуйте функцию
-    return ""
+
+    return str(uuid.uuid4())
 
 
 def create_product(
@@ -73,8 +73,25 @@ def create_product(
         and ``product_names`` are left unchanged and an explanatory
         message is printed.
     """
-    # TODO: реализуйте функцию
-    return ""
+    new_name = normalize_product_name(fields.get(NAME_KEY, ""))
+
+    if not new_name:
+        return print("product name must not be blank")
+
+    if new_name in product_names:
+        return print(f"product name '{new_name}' is already taken")
+
+    new_id = generate_product_id()
+    new_price = normalize_price(fields.get(PRICE_KEY, 0))
+    storage[new_id] = {
+        NAME_KEY: new_name,
+        PRICE_KEY: new_price,
+        QUANTITY_KEY: fields.get(QUANTITY_KEY, 0),
+    }
+
+    product_names.add(new_name)
+
+    return new_id
 
 
 def read_product(storage: dict[str, Product], product_id: str) -> Product | None:
@@ -88,8 +105,10 @@ def read_product(storage: dict[str, Product], product_id: str) -> Product | None
         The matching product record, or ``None`` when no product carries
         that identifier (a message is printed in that case).
     """
-    # TODO: реализуйте функцию
-    return {}
+
+    if product := storage.get(product_id):
+        return product
+    return print(f"no product with id {product_id}")
 
 
 def update_product(
@@ -129,8 +148,27 @@ def update_product(
         and an explanatory message is printed. Renaming a product to its
         own current name is allowed.
     """
-    # TODO: реализуйте функцию
-    return {}
+    if not (old_product := storage.get(product_id)):
+        return print(f"no product with id {product_id}")
+
+    if NAME_KEY in fields:
+        new_name = fields.get(NAME_KEY, "")
+        new_name = normalize_product_name(new_name)
+        fields[NAME_KEY] = new_name
+        if not new_name:
+            return print("product name must not be blank")
+        if new_name != old_product[NAME_KEY] and new_name in product_names:
+            return print(f"product name '{new_name}' is already taken")
+        if new_name != old_product[NAME_KEY]:
+            product_names.remove(old_product[NAME_KEY])
+            product_names.add(new_name)
+
+    if PRICE_KEY in fields:
+        fields[PRICE_KEY] = normalize_price(fields[PRICE_KEY])
+
+    old_product.update(fields)
+
+    return old_product
 
 
 def delete_product(
@@ -153,5 +191,8 @@ def delete_product(
         product carried that identifier (``storage`` and ``product_names``
         are left unchanged and a message is printed).
     """
-    # TODO: реализуйте функцию
-    return ""
+    if product := storage.get(product_id):
+        product_names.remove(product[NAME_KEY])
+        del storage[product_id]
+        return product_id
+    return print(f"no product with id {product_id}")
diff --git a/src/part4/run_admin.py b/src/part4/run_admin.py
index 2247b29b..2bb08fb2 100644
--- a/src/part4/run_admin.py
+++ b/src/part4/run_admin.py
@@ -28,22 +28,32 @@
 is left untouched and the loop keeps running; only ``exit`` stops it.
 """
 
-from decimal import Decimal, InvalidOperation  # noqa: F401
+from decimal import Decimal, InvalidOperation
 from typing import Final
 
-from .crud import (  # noqa: F401
+from .crud import (
     create_product,
     delete_product,
     read_product,
     update_product,
 )
-from .storage import NAME_KEY, PRICE_KEY, QUANTITY_KEY, Product  # noqa: F401
-from .utils import get_storage_str_representation  # noqa: F401
+from .storage import NAME_KEY, PRICE_KEY, QUANTITY_KEY, Product
+from .utils import get_storage_str_representation
 
 
-# TODO: задайте приглашение и текст справки (используйте своё решение части 3)
-PROMPT: Final[str] = ""
-HELP_TEXT: Final[str] = ""
+PROMPT: Final[str] = "admin> "
+HELP_TEXT: Final[str] = """Available commands:
+  help                                       show this message
+  exit                                       leave the console
+  show                                       print the whole store as a table
+  create <name...> <price> <quantity>        add a product, print its new id
+  read <id>                                  print the product with that id
+  update <id> <name...> <price> <quantity>   overwrite that product's fields
+  delete <id>                                remove the product with that id
+
+For create and update the price and quantity are the last two words of the
+line; everything before them is the product name, so it may contain spaces
+(for example "Gibson SG Junior") and needs no quoting."""
 
 
 def show_help() -> None:
@@ -53,7 +63,7 @@ def show_help() -> None:
     is: a heading, one line per command with a short description, and a
     note on how multi-word names are parsed.
     """
-    # TODO: реализуйте функцию (используйте своё решение части 3)
+    print(HELP_TEXT)
 
 
 def print_result(result: object) -> None:
@@ -64,7 +74,8 @@ def print_result(result: object) -> None:
             operation already reported its own failure, so nothing is
             printed in that case.
     """
-    # TODO: реализуйте функцию (используйте своё решение части 3)
+    if result is not None:
+        print(result)
 
 
 def run_command(
@@ -91,8 +102,50 @@ def run_command(
         decimal.InvalidOperation: If the price argument of ``create`` or
             ``update`` does not parse as a decimal number.
     """
-    # TODO: реализуйте функцию
-    return False
+    match line.split():
+        case ["help"]:
+            show_help()
+
+        case ["exit"]:
+            return False
+
+        case ["show"]:
+            print(get_storage_str_representation(storage))
+
+        case ["read", product_id]:
+            print_result(read_product(storage, product_id))
+
+        case ["delete", product_id]:
+            print_result(delete_product(storage, product_names, product_id))
+
+        case ["create", *name_parts, price, quantity] if name_parts:
+            name = " ".join(name_parts)
+            price_decimal = Decimal(price)
+            quantity_int = int(quantity)
+
+            fields = {
+                NAME_KEY: name,
+                PRICE_KEY: price_decimal,
+                QUANTITY_KEY: quantity_int,
+            }
+
+            print_result(create_product(storage, product_names, fields))
+
+        case ["update", product_id, *name_parts, price, quantity] if name_parts:
+            name = " ".join(name_parts)
+            price_decimal = Decimal(price)
+            quantity_int = int(quantity)
+            fields = {
+                NAME_KEY: name,
+                PRICE_KEY: price_decimal,
+                QUANTITY_KEY: quantity_int,
+            }
+            print_result(update_product(storage, product_names, product_id, fields))
+
+        case _:
+            print(f"'{line}' is not a command")
+
+    return True
 
 
 def main() -> None:
diff --git a/src/part4/storage.py b/src/part4/storage.py
index 9acedf07..a25f6253 100644
--- a/src/part4/storage.py
+++ b/src/part4/storage.py
@@ -40,6 +40,6 @@
 
 # Name of each field inside a Product record.
 # TODO: задайте имена полей записи
-NAME_KEY: Final = ""
-PRICE_KEY: Final = ""
-QUANTITY_KEY: Final = ""
+NAME_KEY: Final = "name"
+PRICE_KEY: Final = "price"
+QUANTITY_KEY: Final = "quantity"
diff --git a/src/part4/utils.py b/src/part4/utils.py
index d2a940ea..d33b6798 100644
--- a/src/part4/utils.py
+++ b/src/part4/utils.py
@@ -18,10 +18,10 @@
   the longest value it holds in that particular call.
 """
 
-from decimal import ROUND_HALF_UP, Decimal  # noqa: F401
+from decimal import ROUND_HALF_UP, Decimal
 from typing import Final
 
-from .storage import (  # noqa: F401
+from .storage import (
     NAME_KEY,
     PRICE_KEY,
     QUANTITY_KEY,
@@ -33,14 +33,14 @@
 # Quantisation step derived from PRICE_PRECISION, e.g. Decimal("0.01").
 # TODO: задайте число знаков после запятой и шаг квантования (используйте своё
 # решение части 3)
-PRICE_PRECISION: Final[int] = 0
-PRICE_STEP: Final = Decimal(0)
+PRICE_PRECISION: Final[int] = 2
+PRICE_STEP: Final = Decimal(1).scaleb(-PRICE_PRECISION)
 
 # Column headers of the table produced by get_storage_str_representation,
 # left to right. The width of each column is not fixed here -- it is
 # measured per call from the data (see the function).
 # TODO: задайте заголовки столбцов таблицы (используйте своё решение части 3)
-TABLE_HEADERS: Final[tuple[str, ...]] = ()
+TABLE_HEADERS: Final[tuple[str, ...]] = ("ID", "name", "price", "quantity")
 
 
 def normalize_price(price: Decimal) -> Decimal:
@@ -53,8 +53,7 @@ def normalize_price(price: Decimal) -> Decimal:
         ``price`` quantised to :data:`PRICE_PRECISION` fractional digits,
         with halves rounded up.
     """
-    # TODO: реализуйте функцию (используйте своё решение части 3)
-    return Decimal(0)
+    return price.quantize(PRICE_STEP, ROUND_HALF_UP)
 
 
 def normalize_product_name(name: str) -> str:
@@ -72,10 +71,7 @@ def normalize_product_name(name: str) -> str:
         whitespace.
     """
     # TODO: реализуйте функцию (используйте своё решение части 3)
-    return ""
-
-
-# TODO: при необходимости добавьте свои вспомогательные функции
+    return " ".join(name.split()).lower()
 
 
 def get_storage_str_representation(storage: dict[str, Product]) -> str:
@@ -96,5 +92,36 @@ def get_storage_str_representation(storage: dict[str, Product]) -> str:
         ``storage`` is empty only the header and separator rows are
         returned, sized to the header labels.
     """
-    # TODO: реализуйте функцию (используйте своё решение части 3)
-    return ""
+
+    rows = []
+    for product_id, product in storage.items():
+        rows.append(
+            (
+                product_id,
+                product[NAME_KEY],
+                str(product[PRICE_KEY]),
+                str(product[QUANTITY_KEY]),
+            )
+        )
+    columns = tuple(zip(TABLE_HEADERS, *rows))
+
+    column_width = [max(map(len, column)) for column in columns]
+
+    header = (
+        "| "
+        + " | ".join(
+            f"{value:<{width}}" for value, width in zip(TABLE_HEADERS, column_width)
+        )
+        + " | "
+    )
+
+    separator = "|" + "|".join("-" * (width + 2) for width in column_width) + "|"
+
+    formatted_rows = [
+        "| "
+        + " | ".join(f"{value:<{width}}" for value, width in zip(row, column_width))
+        + " |"
+        for row in rows
+    ]
+
+    return "\n".join([header, separator, *formatted_rows])
diff --git a/test b/test
new file mode 100644
index 00000000..fedebcc1
--- /dev/null
+++ b/test
@@ -0,0 +1,5 @@
+x = 0b1101
+y = bin(x)
+print(x)
+print(bin(x))   
+print(int(y))
\ No newline at end of file
diff --git a/uv.lock b/uv.lock
index 2a56c481..b51f5004 100644
--- a/uv.lock
+++ b/uv.lock
@@ -1,5 +1,5 @@
 version = 1
-revision = 2
+revision = 3
 requires-python = ">=3.12"
 resolution-markers = [
     "python_full_version >= '3.15'",
@@ -70,6 +70,24 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/91/a7/c8bbb2173f7a7131b3b2412035b2d814ab5ef2ce9799bd06f07c451640e4/ast_serialize-0.11.2-cp39-abi3-win_arm64.whl", hash = "sha256:dab599cbdcb7b45b18c41fad746645580b3a24357082b7f0e8921cd373804f27", size = 1136031, upload-time = "2026-09-13T18:48:54.04Z" },
 ]
 
+[[package]]
+name = "colorama"
+version = "0.4.6"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/d8/53/6f443c9a4a8358a93a6792e2acffb9d9d5cb0a5cfd8802644b7b1c9a02e4/colorama-0.4.6.tar.gz", hash = "sha256:08695f5cb7ed6e0531a20572697297273c47b8cae5a63ffc6d6ed5c201be6e44", size = 27697, upload-time = "2022-10-25T02:36:22.414Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/d1/d6/3965ed04c63042e047cb6a3e6ed1a63a35087b6a609aa3a15ed8ac56c221/colorama-0.4.6-py2.py3-none-any.whl", hash = "sha256:4f1d9991f5acc0ca119f9d443620b77f9d6b33703e51011c16baf57afb285fc6", size = 25335, upload-time = "2022-10-25T02:36:20.889Z" },
+]
+
+[[package]]
+name = "iniconfig"
+version = "2.3.1"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/01/e1/2069291243c926a2ff1cd706c7f3eeb9b62144bf60f77c9fb9ff2fb26bd3/iniconfig-2.3.1.tar.gz", hash = "sha256:67f4b9c50da0dedf52af349e7749a80a9057a5031199791b906c3bb3ae878960", size = 21209, upload-time = "2026-10-06T22:48:38.076Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/56/43/4ca9e49d27a1fcf6bece6f6aec0ea46bb9112489b93d4b688fb415457bdb/iniconfig-2.3.1-py3-none-any.whl", hash = "sha256:9121e2c1fdb355232495be3194c8dfe87ccc2d5dee45947b78e68f499790d7a7", size = 7552, upload-time = "2026-10-06T22:48:36.959Z" },
+]
+
 [[package]]
 name = "librt"
 version = "0.15.0"
@@ -234,6 +252,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/79/7b/2c79738432f5c924bef5071f933bcc9efd0473bac3b4aa584a6f7c1c8df8/mypy_extensions-1.1.0-py3-none-any.whl", hash = "sha256:1be4cccdb0f2482337c4743e60421de3a356cd97508abadd57d47403e94f5505", size = 4963, upload-time = "2025-04-22T14:54:22.983Z" },
 ]
 
+[[package]]
+name = "packaging"
+version = "26.3"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/7d/fa/3944b40b07da9ce895c0e6303a5ab7d53da063554f534556b134a54d6093/packaging-26.3.tar.gz", hash = "sha256:94edc256424af38762eb31306eed28beb9f0efc50a8837492c9d6fd6004aed79", size = 313412, upload-time = "2026-08-04T18:15:28.737Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/63/34/ba1c580383c9eada3711951fef0795c80b829a078d72188184bcab9dd527/packaging-26.3-py3-none-any.whl", hash = "sha256:d7193f7c8e4e93f444fde0262bf90af30e16fa0ad0ad44cb553c87339b23cd1c", size = 129956, upload-time = "2026-08-04T18:15:27.159Z" },
+]
+
 [[package]]
 name = "pathspec"
 version = "1.1.1"
@@ -251,6 +278,7 @@ source = { virtual = "." }
 [package.dev-dependencies]
 dev = [
     { name = "mypy" },
+    { name = "pytest" },
     { name = "ruff" },
 ]
 
@@ -259,9 +287,44 @@ dev = [
 [package.metadata.requires-dev]
 dev = [
     { name = "mypy", specifier = "==2.3.1" },
+    { name = "pytest", specifier = ">=9.1.1" },
     { name = "ruff", specifier = "==0.16.8" },
 ]
 
+[[package]]
+name = "pluggy"
+version = "1.6.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/f9/e2/3e91f31a7d2b083fe6ef3fa267035b518369d9511ffab804f839851d2779/pluggy-1.6.0.tar.gz", hash = "sha256:7dcc130b76258d33b90f61b658791dede3486c3e6bfb003ee5c9bfb396dd22f3", size = 69412, upload-time = "2025-05-15T12:30:07.975Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/54/20/4d324d65cc6d9205fabedc306948156824eb9f0ee1633355a8f7ec5c66bf/pluggy-1.6.0-py3-none-any.whl", hash = "sha256:e920276dd6813095e9377c0bc5566d94c932c33b27a3e3945d8389c374dd4746", size = 20538, upload-time = "2025-05-15T12:30:06.134Z" },
+]
+
+[[package]]
+name = "pygments"
+version = "2.21.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/49/2e/ced460408999b33da6b31b0021b0f37d329e202d4169aeb164493778f25b/pygments-2.21.0.tar.gz", hash = "sha256:610ca751c9bc2492b38eb9a38a7fbc93edbbb2d7182edaf34e66ae493dee5c8c", size = 5005329, upload-time = "2026-08-17T08:02:48.824Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/71/46/17f022dd3e953bf20a04a028a21ec746d942f8d2af30fa0f124fa0e6a684/pygments-2.21.0-py3-none-any.whl", hash = "sha256:2363c69b61c4a97c838da3b130dcd6468f4848992b21a82f2a63ec34377137d9", size = 1250147, upload-time = "2026-08-17T08:02:44.912Z" },
+]
+
+[[package]]
+name = "pytest"
+version = "9.1.1"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "colorama", marker = "sys_platform == 'win32'" },
+    { name = "iniconfig" },
+    { name = "packaging" },
+    { name = "pluggy" },
+    { name = "pygments" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/e4/47/b9efed96c114afcfa3c9d3fe98a76a1d14c74a9e266d397cf6eb64be5e01/pytest-9.1.1.tar.gz", hash = "sha256:1088fbde8f2b49d95a549a195707afa7a76a3ce9bcadc26b6d71f0ffda5fe313", size = 1636369, upload-time = "2026-06-19T10:58:32.857Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/24/25/1de2678b631f5a49215c6c96fff41ba892b0a34df68d6d80292b1b48aa7f/pytest-9.1.1-py3-none-any.whl", hash = "sha256:37a86b45efb9a47a61a36449063e8e18d0cab3161329fc099eb21783169c4f0c", size = 386536, upload-time = "2026-06-19T10:58:31.347Z" },
+]
+
 [[package]]
 name = "ruff"
 version = "0.16.8"