diff --git a/src/part1/constants.py b/src/part1/constants.py
index 9abfbba2..d9f6e444 100644
--- a/src/part1/constants.py
+++ b/src/part1/constants.py
@@ -1,17 +1,3 @@
-"""Bit layout and default epoch for the Twitter Snowflake ID generator.
-
-A Snowflake identifier is a 63-bit positive integer packed as follows, from
-the most significant bit downwards:
-
-    1 bit   unused sign bit, always zero
-    41 bits milliseconds elapsed since a custom epoch
-    10 bits node identifier
-    12 bits per-millisecond sequence counter
-
-The shift and mask constants should be derived from the bit widths so that
-changing a width keeps everything else consistent.
-"""
-
 from typing import Final
 
 
@@ -19,20 +5,20 @@
 # 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] = 2**TIMESTAMP_BITS - 1
+NODE_ID_MAX: Final[int] = 2**NODE_ID_BITS - 1
+SEQUENCE_ID_MAX: Final[int] = 2**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..491c5a9d 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -1,85 +1,36 @@
-"""Twitter Snowflake identifier generator.
+import time
 
-Snowflake produces roughly time-ordered 64-bit integer identifiers without
-coordination between nodes. Each identifier packs the milliseconds elapsed
-since a custom epoch, a node identifier and a per-millisecond sequence counter
-into a single 63-bit positive integer (see ``constants`` for the layout).
-
-The public entry point is :func:`generate_snowflake_id`. It is stateless: the
-caller passes the sequence counter on every call and is responsible for
-advancing it within a millisecond and resetting it when the clock ticks over.
-
-Each packed field can be read back on its own with :func:`decode_timestamp_ms`,
-:func:`decode_node_id` and :func:`decode_sequence_id`.
-"""
-
-import time  # noqa: F401
-
-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
+    now_ms = (time.time_ns()) // 1_000_000
+    return now_ms - epoch_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).
+    relative_time_ms = snowflake_id >> (NODE_ID_BITS + SEQUENCE_ID_BITS)
+    absolute_time_ms = relative_time_ms + epoch_ms
 
-    Returns:
-        The absolute Unix time in milliseconds at which the identifier was
-        generated.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    return absolute_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 >> SEQUENCE_ID_BITS) & NODE_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 +38,22 @@ 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):
+        print(f"node_id must be in [0, {NODE_ID_MAX}]  your node_id is {node_id}")
+        return None
+    elif not (0 <= sequence_id <= SEQUENCE_ID_MAX):
+        print(
+            f"sequence_id must be in [0, {SEQUENCE_ID_MAX}] your sequence_id is {sequence_id}"
+        )
+        return None
+    else:
+        if 0 <= read_current_millis(epoch_ms) <= TIMESTAMP_MS_MAX:
+            snowflake_id = (
+                read_current_millis(epoch_ms) << (NODE_ID_BITS + SEQUENCE_ID_BITS)
+                | (node_id << SEQUENCE_ID_BITS)
+                | (sequence_id)
+            )
+            return snowflake_id
+        else:
+            print("overflofws")
+            return None
diff --git a/src/part2/cart.py b/src/part2/cart.py
index 063f9aea..559c89c0 100644
--- a/src/part2/cart.py
+++ b/src/part2/cart.py
@@ -11,8 +11,8 @@
 
 from typing import Final
 
-from .crud import read_product, update_product  # noqa: F401
-from .storage import (  # noqa: F401
+from .crud import read_product, update_product
+from .storage import (
     NAME_INDEX,
     PRICE_INDEX,
     QUANTITY_INDEX,
@@ -22,9 +22,16 @@
 
 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 cartline in cart:
+        if cartline[LINE_PRODUCT_ID_INDEX] == product_id:
+            return cartline
+    return None
 
 
 def add_to_cart(
@@ -33,28 +40,37 @@ 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
+
+    storage_quantity = product[QUANTITY_INDEX]
+    if quantity > storage_quantity:
+        print(
+            f"not enough stock for product <{product_id}>: <{product[QUANTITY_INDEX]}> avaiable, <{quantity}> requested"
+        )
+        return None
+    fields = (
+        product[NAME_INDEX],
+        product[PRICE_INDEX],
+        product[QUANTITY_INDEX] - quantity,
+    )
+    update_product(storage, product_id, fields)
+
+    existing_line = find_cart_line(cart, product_id)
+    if existing_line is not None:
+        new_cart_quantity = existing_line[LINE_QUANTITY_INDEX] + quantity
+        new_line = (product_id, new_cart_quantity)
+        for index, line in enumerate(cart):
+            if line[LINE_PRODUCT_ID_INDEX] == product_id:
+                cart[index] = new_line
+                break
+    else:
+        new_line = (product_id, quantity)
+        cart.append(new_line)
+        return new_line
+
+    return new_line
 
 
 def remove_from_cart(
@@ -63,27 +79,42 @@ 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)
+    cart_line = find_cart_line(cart, product_id)
+    if cart_line is None:
+        print(f"product <{product_id}> is not in the cart")
+        return None
+
+    cart_quantity = cart_line[LINE_QUANTITY_INDEX]
+    if cart_quantity < quantity:
+        print(
+            f"cart holds only {cart_quantity} unit(s) of product <{product_id}>, "
+            f"cannot remove {quantity}"
+        )
+        return None
+
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+
+    new_stock_quantity = product[QUANTITY_INDEX] + quantity
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], new_stock_quantity),
+    )
+
+    new_cart_quantity = cart_quantity - quantity
+    if new_cart_quantity == 0:
+        for index, line in enumerate(cart):
+            if line[LINE_PRODUCT_ID_INDEX] == product_id:
+                cart.pop(index)
+                break
+        return (product_id, 0)
+
+    new_line = (product_id, new_cart_quantity)
+    for index, line in enumerate(cart):
+        if line[LINE_PRODUCT_ID_INDEX] == product_id:
+            cart[index] = new_line
+            break
+
+    return new_line
diff --git a/src/part2/crud.py b/src/part2/crud.py
index d026cbcb..8c6c971b 100644
--- a/src/part2/crud.py
+++ b/src/part2/crud.py
@@ -14,66 +14,52 @@
 
 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``.
+def product_in_storage(storage: list[Product], product_id: int) -> int | None:
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            return storage.index(product)
+    return None
 
-    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
+def generate_product_id(storage: list[Product]) -> int:
+    if not storage:
+        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.
+    name, price, quantity = fields
 
-    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.
+    for product in storage:
+        if product[NAME_INDEX] == name:
+            print(f"product name <'{name}'> is already taken")
+            return None
 
-    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
+    product_id = generate_product_id(storage)
+    product_price = normalize_price(price)
+    new_product = (product_id, name, product_price, quantity)
+    storage.append(new_product)
+    return product_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.
+    product_index = product_in_storage(storage, product_id)
+    if product_index is not None:
+        return storage[product_index]
 
-    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)
+    print(f"no product with id <{product_id}>")
+    return None
 
 
 def update_product(
@@ -81,40 +67,23 @@ def update_product(
     product_id: int,
     fields: tuple[str, Decimal, int],
 ) -> Product | None:
-    """Overwrite the fields of the product stored under ``product_id``.
+    name, price, quantity = fields
 
-    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)
+    product_index = product_in_storage(storage, product_id)
+    if product_index is not None:
+        new_price = normalize_price(price)
+        updated_product = (product_id, name, new_price, quantity)
+        storage[product_index] = updated_product
+        return updated_product
+    print(f"no product with id <{product_id}>")
+    return None
 
 
 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
+    product_index = product_in_storage(storage, product_id)
+    if product_index is not None:
+        del storage[product_index]
+        return product_id
+
+    print(f"no products with id <{product_id}>")
+    return None
diff --git a/src/part2/storage.py b/src/part2/storage.py
index b63d5fc7..1a0d6d69 100644
--- a/src/part2/storage.py
+++ b/src/part2/storage.py
@@ -25,10 +25,11 @@
 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..aa36addc 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, rounding=(ROUND_HALF_UP))
diff --git a/src/part3/crud.py b/src/part3/crud.py
index 68811d7e..6cb824ad 100644
--- a/src/part3/crud.py
+++ b/src/part3/crud.py
@@ -20,68 +20,56 @@
 
 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``.
+def product_in_storage(storage: list[Product], product_id: int) -> int | None:
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            return storage.index(product)
+    return None
 
-    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
+def generate_product_id(storage: list[Product]) -> int:
+    if not storage:
+        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
 
+    product_name = normalize_product_name(name)
+    if not product_name:
+        print("product name must not be blank")
+        return None
+    for product in storage:
+        if product[NAME_INDEX] == product_name:
+            print(f"product name '{product_name}' is already taken")
+            return None
 
-def read_product(storage: list[Product], product_id: int) -> Product | None:
-    """Return the product stored under ``product_id``.
+    product_id = generate_product_id(storage)
+    product_price = normalize_price(price)
+    new_product = (product_id, product_name, product_price, quantity)
+    storage.append(new_product)
+    return 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)
+def read_product(storage: list[Product], product_id: int) -> Product | None:
+    product_index = product_in_storage(storage, product_id)
+    if product_index is not None:
+        return storage[product_index]
+
+    print(f"no product with id {product_id}")
+    return None
 
 
 def update_product(
@@ -89,43 +77,35 @@ 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
+    normalize_name = normalize_product_name(name)
+    if not normalize_name:
+        print("product name must not be blank")
+        return None
+
+    product_index = product_in_storage(storage, product_id)
+    if product_index is None:
+        print(f"no product with id {product_id}")
+        return None
+
+    for product in storage:
+        if (product[NAME_INDEX] == normalize_name) and (
+            product_id != product[PRODUCT_ID_INDEX]
+        ):
+            print(f"product name '{normalize_name}' is already taken")
+            return None
+
+    new_price = normalize_price(price)
+    updated_product = (product_id, normalize_name, new_price, quantity)
+    storage[product_index] = 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
+    product_index = product_in_storage(storage, product_id)
+    if product_index is not None:
+        del storage[product_index]
+        return product_id
+
+    print(f"no product with id {product_id}")
+    return None
diff --git a/src/part3/run_admin.py b/src/part3/run_admin.py
index c5feeb0b..3f849339 100644
--- a/src/part3/run_admin.py
+++ b/src/part3/run_admin.py
@@ -29,67 +29,67 @@
 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
-
-
-# TODO: задайте приглашение и текст справки
-PROMPT: Final[str] = ""
-HELP_TEXT: Final[str] = ""
+from .utils import get_storage_str_representation
+
+
+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
+    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.
-
-    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.
-
-    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``.
-
-    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
+    match line.split():
+        case ["help"]:
+            print(HELP_TEXT)
+        case ["exit"]:
+            return False
+        case ["show"]:
+            print(get_storage_str_representation(storage))
+        case ["create", part_name, *other_part_name, price, quantity]:
+            name = " ".join([part_name] + other_part_name)
+            new_product = (name, Decimal(price), int(quantity))
+            print_result(create_product(storage, new_product))
+        case ["read", id_product]:
+            print_result(read_product(storage, int(id_product)))
+        case ["update", id_product, part_name, *other_part_name, price, quantity]:
+            name = " ".join([part_name] + other_part_name)
+            new_product = (name, Decimal(price), int(quantity))
+            print_result(update_product(storage, int(id_product), new_product))
+        case ["delete", id_product]:
+            print_result(delete_product(storage, int(id_product)))
+        case _:
+            print(f"'{line}' is not a command")
+    return True
 
 
 def main() -> None:
diff --git a/src/part3/storage.py b/src/part3/storage.py
index c5e34be5..7ee8d48d 100644
--- a/src/part3/storage.py
+++ b/src/part3/storage.py
@@ -24,12 +24,12 @@
 
 type Product = tuple[int, str, Decimal, int]
 
-# TODO: задайте позиции полей внутри кортежа Product (используйте своё решение
-# части 2)
+# 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/part3/utils.py b/src/part3/utils.py
index 318ded0b..90de81ae 100644
--- a/src/part3/utils.py
+++ b/src/part3/utils.py
@@ -18,78 +18,51 @@
   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
+from .storage import (
+    NAME_INDEX,
+    PRICE_INDEX,
+    PRODUCT_ID_INDEX,
+    QUANTITY_INDEX,
+    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")
 
-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, rounding=(ROUND_HALF_UP))
 
 
 def normalize_product_name(name: str) -> str:
-    """Reduce a product name to the canonical form the store keeps.
+    return " ".join(name.split()).lower()
 
-    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 ""
+def get_storage_str_representation(storage: list[Product]) -> str:
+    def product_to_row(point: Product) -> tuple[str, ...]:
+        return (
+            str(point[PRODUCT_ID_INDEX]),
+            point[NAME_INDEX],
+            str(point[PRICE_INDEX]),
+            str(point[QUANTITY_INDEX]),
+        )
 
+    rows = [TABLE_HEADERS] + [product_to_row(p) for p in storage]
 
-# TODO: при необходимости добавьте свои вспомогательные функции
+    widths = [max(len(row[i]) for row in rows) for i in range(len(TABLE_HEADERS))]
 
+    def format_row(row: tuple[str, ...]) -> str:
+        return "| " + " | ".join(v.ljust(w) for v, w in zip(row, widths)) + " |"
 
-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 ""
+    separator = "|-" + "-|-".join("-" * w for w in widths) + "-|"
+
+    lines = [format_row(rows[0]), separator]
+    lines.extend(format_row(r) for r in rows[1:])
+    return "\n".join(lines)
diff --git a/src/part4/cart.py b/src/part4/cart.py
index aed9bb72..b74fbea6 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
@@ -22,32 +22,18 @@ def add_to_cart(
     product_id: str,
     quantity: int,
 ) -> int | 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 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
-    gains ``quantity`` units of ``product_id`` -- the product is added when
-    the cart had none of it.
-
-    Args:
-        storage: The product store to draw stock from; modified in place on
-            success.
-        product_names: The normalised names in ``storage``; a
-            quantity-only change never renames a product, so it is left
-            unchanged here.
-        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 quantity of ``product_id`` in the cart after the addition, or
-        ``None`` when the product is unknown or the store cannot cover the
-        request.
-    """
-    # TODO: реализуйте функцию
-    return 0
+    if product_id not in storage:
+        print(f"no product with id {product_id}")
+        return None
+    available_stock = storage[product_id][QUANTITY_KEY]
+    if available_stock < quantity:
+        print(
+            f"not enough stock for product {product_id}: {available_stock} available, {quantity} requested"
+        )
+        return None
+    storage[product_id][QUANTITY_KEY] -= quantity
+    cart[product_id] = cart.get(product_id, 0) + quantity
+    return cart[product_id]
 
 
 def remove_from_cart(
@@ -57,31 +43,21 @@ def remove_from_cart(
     product_id: str,
     quantity: int,
 ) -> int | None:
-    """Move ``quantity`` units of ``product_id`` from ``cart`` back to the store.
-
-    If the cart holds no units of ``product_id``, a message is printed and
-    nothing changes. If it holds fewer units than requested, an explanatory
-    message is printed and nothing changes. If the product is missing from
-    ``storage``, a message is printed and nothing changes. Otherwise the cart loses
-    ``quantity`` units of the product -- the product is dropped from the
-    cart when its quantity reaches zero -- and the store record gains
-    ``quantity`` units back.
-
-    Args:
-        storage: The product store to return stock to; modified in place on
-            success.
-        product_names: The normalised names in ``storage``; a
-            quantity-only change never renames a product, so it is left
-            unchanged here.
-        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 quantity of ``product_id`` left in the cart after the removal
-        (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:
+        print(f"product {product_id} is not in the cart")
+        return None
+    in_cart = cart[product_id]
+    if in_cart < quantity:
+        print(
+            f"cart holds only {in_cart} unit(s) of product {product_id}, cannot remove {quantity}"
+        )
+        return None
+    if product_id not in storage:
+        print(f"no product with id {product_id}")
+        return None
+    storage[product_id][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..249d7367 100644
--- a/src/part4/crud.py
+++ b/src/part4/crud.py
@@ -23,26 +23,19 @@
 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:
-    """Generate an identifier for a new product.
-
-    Returns:
-        A freshly generated UUID, stringified.
-    """
-    # TODO: реализуйте функцию
-    return ""
+    return str(uuid.uuid4())
 
 
 def create_product(
@@ -50,46 +43,27 @@ def create_product(
     product_names: set[str],
     fields: dict[str, Any],
 ) -> str | None:
-    """Add a new product to ``storage`` and return its new identifier.
-
-    Args:
-        storage: The product store to add to; modified in place on
-            success.
-        product_names: The normalised names already in ``storage``; the
-            new name is added to it in place on success.
-        fields: A dictionary with the ``name``, ``price`` and ``quantity``
-            keys (see :data:`~src.part4.storage.NAME_KEY`,
-            :data:`~src.part4.storage.PRICE_KEY` and
-            :data:`~src.part4.storage.QUANTITY_KEY`) 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``
-        and ``product_names`` are left unchanged and an explanatory
-        message is printed.
-    """
-    # TODO: реализуйте функцию
-    return ""
+    normalize_name = normalize_product_name(fields[NAME_KEY])
+    if not normalize_name:
+        print("product name must not be blank")
+        return None
+    if normalize_name in product_names:
+        print(f'product name "{normalize_name}" is already taken')
+        return None
+    product_id = generate_product_id()
+    new_product = fields.copy()
+    new_product[NAME_KEY] = normalize_name
+    new_product[PRICE_KEY] = normalize_price(fields[PRICE_KEY])
+    storage[product_id] = new_product
+    product_names.add(normalize_name)
+    return product_id
 
 
 def read_product(storage: dict[str, Product], product_id: str) -> 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 record, or ``None`` when no product carries
-        that identifier (a message is printed in that case).
-    """
-    # TODO: реализуйте функцию
-    return {}
+    if product_id not in storage:
+        print(f"no product with id {product_id}")
+        return None
+    return storage[product_id]
 
 
 def update_product(
@@ -98,39 +72,27 @@ def update_product(
     product_id: str,
     fields: dict[str, Any],
 ) -> Product | None:
-    """Overwrite the fields of the product stored under ``product_id``.
-
-    The identifier itself is preserved. ``fields`` may carry any subset of
-    ``name``, ``price`` and ``quantity``; a key that is missing keeps the
-    value the product already has, so a caller can update a single field
-    without repeating the other two.
-
-    Args:
-        storage: The product store to modify; the matching record is
-            updated in place on success.
-        product_names: The normalised names already in ``storage``; on a
-            successful rename the old name is removed from it and the new
-            one added.
-        product_id: The identifier of the product to change.
-        fields: A dictionary with any of the ``name``, ``price`` and
-            ``quantity`` keys (see :data:`~src.part4.storage.NAME_KEY`,
-            :data:`~src.part4.storage.PRICE_KEY` and
-            :data:`~src.part4.storage.QUANTITY_KEY`) holding the new
-            values. ``price`` is a :class:`~decimal.Decimal` amount and is
-            rounded to the stored money precision before it is saved.
-            Mutated in place: a ``name`` or ``price`` value present in
-            ``fields`` is overwritten with its normalised form.
-
-    Returns:
-        The updated product record, or ``None`` when ``name`` is present
-        and blank once normalised, no product carries that identifier, or
-        the normalised name is already taken by another product. In every
-        ``None`` case ``storage`` and ``product_names`` are left unchanged
-        and an explanatory message is printed. Renaming a product to its
-        own current name is allowed.
-    """
-    # TODO: реализуйте функцию
-    return {}
+    if product_id not in storage:
+        print(f"no product with id {product_id}")
+        return None
+    product = storage[product_id]
+    old_name = product[NAME_KEY]
+    if NAME_KEY in fields:
+        normalized_name = normalize_product_name(fields[NAME_KEY])
+        if not normalized_name:
+            print("product name must not be blank")
+            return None
+        if normalized_name != old_name and normalized_name in product_names:
+            print(f'product name "{normalized_name}" is already taken')
+            return None
+        if normalized_name != old_name:
+            product_names.discard(old_name)
+            product_names.add(normalized_name)
+        fields[NAME_KEY] = normalized_name
+    if PRICE_KEY in fields:
+        fields[PRICE_KEY] = normalize_price(fields[PRICE_KEY])
+    product.update(fields)
+    return storage[product_id]
 
 
 def delete_product(
@@ -138,20 +100,10 @@ def delete_product(
     product_names: set[str],
     product_id: str,
 ) -> str | None:
-    """Remove the product stored under ``product_id`` from ``storage``.
-
-    Args:
-        storage: The product store to remove from; modified in place on
-            success.
-        product_names: The normalised names already in ``storage``; the
-            departing product's name is removed from it 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`` and ``product_names``
-        are left unchanged and a message is printed).
-    """
-    # TODO: реализуйте функцию
-    return ""
+    if product_id not in storage:
+        print(f"no product with id {product_id}")
+        return None
+    product_name = storage[product_id][NAME_KEY]
+    product_names.discard(product_name)
+    del storage[product_id]
+    return product_id
diff --git a/src/part4/run_admin.py b/src/part4/run_admin.py
index 2247b29b..a75f2d85 100644
--- a/src/part4/run_admin.py
+++ b/src/part4/run_admin.py
@@ -28,71 +28,78 @@
 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:
-    """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 (используйте своё решение части 3)
+    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 (используйте своё решение части 3)
+    if result is not None:
+        print(result)
 
 
 def run_command(
     storage: dict[str, Product], product_names: set[str], line: str
 ) -> bool:
-    """Parse one console line and carry out the command it names.
-
-    Args:
-        storage: The product store shared across the session; mutated in
-            place by the ``create``, ``update`` and ``delete`` commands.
-        product_names: The normalised names already in ``storage``; kept
-            in sync by the ``create``, ``update`` and ``delete`` commands.
-        line: One line of console input, already stripped of surrounding
-            whitespace.
-
-    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``.
-
-    Raises:
-        ValueError: If the 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
+    match line.split():
+        case ["help"]:
+            print(HELP_TEXT)
+        case ["exit"]:
+            return False
+        case ["show"]:
+            print(get_storage_str_representation(storage))
+        case ["create", part_name, *other_part_name, price, quantity]:
+            name = " ".join([part_name] + other_part_name)
+            fields = {
+                NAME_KEY: name,
+                PRICE_KEY: Decimal(price),
+                QUANTITY_KEY: int(quantity),
+            }
+            print_result(create_product(storage, product_names, fields))
+        case ["read", id_product]:
+            print_result(read_product(storage, id_product))
+        case ["update", id_product, part_name, *other_part_name, price, quantity]:
+            name = " ".join([part_name] + other_part_name)
+            fields = {
+                NAME_KEY: name,
+                PRICE_KEY: Decimal(price),
+                QUANTITY_KEY: int(quantity),
+            }
+            print_result(update_product(storage, product_names, id_product, fields))
+        case ["delete", id_product]:
+            print_result(delete_product(storage, product_names, id_product))
+        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..15e0ace1 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,
@@ -33,68 +33,44 @@
 # 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:
-    """Round a price to the precision every stored record uses.
+    return price.quantize(PRICE_STEP, rounding=(ROUND_HALF_UP))
 
-    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 3)
-    return Decimal(0)
+def normalize_product_name(name: str) -> str:
+    return " ".join(name.split()).lower()
 
 
-def normalize_product_name(name: str) -> str:
-    """Reduce a product name to the canonical form the store keeps.
+# TODO: при необходимости добавьте свои вспомогательные функции
 
-    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 (используйте своё решение части 3)
-    return ""
+def get_storage_str_representation(storage: dict[str, Product]) -> str:
+    def product_to_row(product_id: str, product: Product) -> tuple[str, ...]:
+        return (
+            str(product_id),
+            str(product[NAME_KEY]),
+            str(product[PRICE_KEY]),
+            str(product[QUANTITY_KEY]),
+        )
 
+    rows = [TABLE_HEADERS] + [product_to_row(cid, c) for cid, c in storage.items()]
+    widths = [max(len(row[i]) for row in rows) for i in range(len(TABLE_HEADERS))]
 
-# TODO: при необходимости добавьте свои вспомогательные функции
+    def format_row(row: tuple[str, ...]) -> str:
+        return "| " + " | ".join(v.ljust(w) for v, w in zip(row, widths)) + " |"
 
+    separator = "|-" + "-|-".join("-" * w for w in widths) + "-|"
 
-def get_storage_str_representation(storage: dict[str, 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 insertion order. When
-        ``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 ""
+    lines = [format_row(rows[0]), separator]
+    lines.extend(format_row(r) for r in rows[1:])
+    return "\n".join(lines)