diff --git a/src/part1/constants.py b/src/part1/constants.py
index 9abfbba2..7a112a77 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] = 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..33b6754b 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -13,12 +13,14 @@
 :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,
 )
@@ -34,8 +36,8 @@ def read_current_millis(epoch_ms: int) -> int:
         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_ms = time.time_ns() // 1_000_000
+    return current_ms - epoch_ms
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
@@ -50,8 +52,10 @@ def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) ->
         The absolute Unix time in milliseconds at which the identifier was
         generated.
     """
-    # TODO: реализуйте функцию
-    return 0
+    bits_shift = NODE_ID_BITS + SEQUENCE_ID_BITS
+    timestamp_part = snowflake_id >> bits_shift
+
+    return timestamp_part + epoch_ms
 
 
 def decode_node_id(snowflake_id: int) -> int:
@@ -64,8 +68,10 @@ def decode_node_id(snowflake_id: int) -> int:
         The node identifier packed into ``snowflake_id``, in the range
         ``[0, NODE_ID_MAX]``.
     """
-    # TODO: реализуйте функцию
-    return 0
+    bits_mask = (1 << NODE_ID_BITS) - 1
+    node_id = (snowflake_id >> SEQUENCE_ID_BITS) & bits_mask
+
+    return node_id
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
@@ -78,8 +84,9 @@ def decode_sequence_id(snowflake_id: int) -> int:
         The per-millisecond sequence counter packed into ``snowflake_id``, in
         the range ``[0, SEQUENCE_ID_MAX]``.
     """
-    # TODO: реализуйте функцию
-    return 0
+    bits_mask = (1 << SEQUENCE_ID_BITS) - 1
+
+    return snowflake_id & bits_mask
 
 
 def generate_snowflake_id(
@@ -110,5 +117,23 @@ def generate_snowflake_id(
         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 node_id < 0 or node_id > NODE_ID_MAX:
+        print(f"node_id must be in [0, {NODE_ID_MAX}], got {node_id}")
+        return None
+
+    if sequence_id < 0 or sequence_id > SEQUENCE_ID_MAX:
+        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], got {sequence_id}")
+        return None
+
+    current_millis = read_current_millis(epoch_ms)
+    if current_millis > TIMESTAMP_MS_MAX:
+        print("TIMESTAMP_MS_MAX overflows")
+        return None
+
+    snowflake_id = (
+        (current_millis << (SEQUENCE_ID_BITS + NODE_ID_BITS))
+        | (node_id << SEQUENCE_ID_BITS)
+        | sequence_id
+    )
+
+    return snowflake_id
diff --git a/src/part2/TASK.md b/src/part2/TASK.md
index 25736d9c..36a83116 100644
--- a/src/part2/TASK.md
+++ b/src/part2/TASK.md
@@ -187,7 +187,7 @@ delete) над единым хранилищем, аккуратная рабо
    печатается сообщение об ошибке, содержащее идентификатор (например:
    `product <id> is not in the cart`), возвращается `None`, ничего не меняется.
 2. Иначе количество в строке корзины сравнивается с запрошенным. Если в корзине
-   строго меньше, чем `quantity` — печатается сообщение об ошибке с
+   строго меньше, чем `quantity` — печатается сообщение об ошибке с   
    идентификатором (например:
    `cart holds only <в корзине> unit(s) of product <id>, cannot remove <quantity>`),
    возвращается `None`, ничего не меняется.
diff --git a/src/part2/cart.py b/src/part2/cart.py
index 063f9aea..ec0c871a 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,
@@ -24,7 +24,7 @@
 
 # TODO: задайте позиции полей внутри кортежа CartLine
 LINE_PRODUCT_ID_INDEX: Final = 0
-LINE_QUANTITY_INDEX: Final = 0
+LINE_QUANTITY_INDEX: Final = 1
 
 
 def add_to_cart(
@@ -53,8 +53,82 @@ def add_to_cart(
         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 not product:
+        return None
+
+    if product[QUANTITY_INDEX] < quantity:
+        print(
+            f"not enough stock for product {product_id}: storage available, {product[QUANTITY_INDEX]} requested"
+        )
+
+        return None
+
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], product[QUANTITY_INDEX] - quantity),
+    )
+
+    for index_cart_line in range(len(cart)):
+        if cart[index_cart_line][LINE_PRODUCT_ID_INDEX] == product_id:
+            cart[index_cart_line] = (
+                product_id,
+                quantity + cart[index_cart_line][LINE_QUANTITY_INDEX],
+            )
+            return cart[index_cart_line]
+
+    cart.append((product_id, quantity))
+    return (product_id, quantity)
+
+
+def find_cart_line(cart: list[CartLine], product_id: int) -> CartLine | None:
+    """Find line of the product from cart
+
+    Find first entry in cart line with necassery product_id.
+
+    Args:
+        cart: user's shopping cart
+        product_id: The identifier of the product to find.
+
+    Returns:
+        cart_line if all correct
+        `None` if identifier of the product don't found
+    """
+    for cart_line in cart:
+        if cart_line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return cart_line
+
+    print(f"product {product_id} is not in the cart")
+    return None
+
+
+def update_cart_line(
+    cart: list[CartLine], product_id: int, quantity: int
+) -> CartLine | None:
+    """Update line of the product in the cart
+
+    If quantity = 0 line in the cart is remove. Else his quantity update.
+
+    Args:
+        cart: user's shopping cart
+        product_id: The identifier of the product to find.
+        quantity: New product quantity value
+
+    Returns:
+        cart_line if all correct
+        `None` if identifier of the product don't found
+    """
+    for index_cart_line in range(len(cart)):
+        if cart[index_cart_line][LINE_PRODUCT_ID_INDEX] == product_id:
+            if quantity == 0:
+                del cart[index_cart_line]
+            else:
+                cart[index_cart_line] = (product_id, quantity)
+            return (product_id, quantity)
+
+    print(f"product {product_id} is not in the cart")
+    return None
 
 
 def remove_from_cart(
@@ -85,5 +159,30 @@ def remove_from_cart(
         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 not cart_line:
+        return None
+
+    if cart_line[LINE_QUANTITY_INDEX] < quantity:
+        print(
+            f"cart holds only {cart_line[LINE_QUANTITY_INDEX]} unit(s) "
+            f"of product {product_id}, cannot remove {quantity}"
+        )
+
+        return None
+
+    product = read_product(storage, product_id)
+    if not product:
+        return None
+
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], product[QUANTITY_INDEX] + quantity),
+    )
+
+    new_cart_line = update_cart_line(
+        cart, product_id, cart_line[LINE_QUANTITY_INDEX] - quantity
+    )
+
+    return new_cart_line
diff --git a/src/part2/crud.py b/src/part2/crud.py
index d026cbcb..48c0ea56 100644
--- a/src/part2/crud.py
+++ b/src/part2/crud.py
@@ -14,13 +14,16 @@
 
 from decimal import Decimal
 
-from .storage import (  # noqa: F401
+from .storage import (
+    FIELDS_NAME_INDEX,
+    FIELDS_PRICE_INDEX,
+    FIELDS_QUANTITY_INDEX,
     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:
@@ -34,8 +37,10 @@ def generate_product_id(storage: list[Product]) -> int:
         :data:`~src.part2.storage.PRODUCT_ID_MIN` when ``storage`` is
         empty.
     """
-    # TODO: реализуйте функцию
-    return 0
+    if not storage:
+        return PRODUCT_ID_MIN
+
+    return max(product[PRODUCT_ID_INDEX] for product in storage) + 1
 
 
 def create_product(
@@ -56,8 +61,18 @@ def create_product(
         ``storage`` is left unchanged and a message naming the clashing
         name is printed.
     """
-    # TODO: реализуйте функцию
-    return 0
+    if any(fields[FIELDS_NAME_INDEX] == product[NAME_INDEX] for product in storage):
+        print(f"product name {fields[FIELDS_NAME_INDEX]} is already taken")
+        return None
+
+    new_id = generate_product_id(storage)
+    new_price = normalize_price(fields[FIELDS_PRICE_INDEX])
+
+    storage.append(
+        (new_id, fields[FIELDS_NAME_INDEX], new_price, fields[FIELDS_QUANTITY_INDEX])
+    )
+
+    return new_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -72,8 +87,12 @@ def read_product(storage: list[Product], product_id: int) -> Product | None:
         ``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
+
+    print(f"no product with id {product_id}")
+    return None
 
 
 def update_product(
@@ -97,10 +116,33 @@ def update_product(
     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).
+        left unchanged and a message is printed). Also ``None`` when
+        product name is already taken.
     """
-    # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    index_modifiable_product = -1
+
+    for index in range(len(storage)):
+        if storage[index][NAME_INDEX] == fields[FIELDS_NAME_INDEX]:
+            print(f"product name {fields[FIELDS_NAME_INDEX]} is already taken")
+            return None
+
+        if storage[index][PRODUCT_ID_INDEX] == product_id:
+            index_modifiable_product = index
+
+    if index_modifiable_product == -1:
+        print(f"no product with id {product_id}")
+        return None
+
+    new_price = normalize_price(fields[FIELDS_PRICE_INDEX])
+
+    storage[index_modifiable_product] = (
+        product_id,
+        fields[FIELDS_NAME_INDEX],
+        new_price,
+        fields[FIELDS_QUANTITY_INDEX],
+    )
+
+    return storage[index_modifiable_product]
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
@@ -116,5 +158,10 @@ def delete_product(storage: list[Product], product_id: int) -> int | None:
         product carried that identifier (``storage`` is left unchanged and
         a message is printed).
     """
-    # TODO: реализуйте функцию
-    return 0
+    for i, product in enumerate(storage):
+        if product[PRODUCT_ID_INDEX] == product_id:
+            del storage[i]
+            return product_id
+
+    print(f"no product with id {product_id}")
+    return None
diff --git a/src/part2/storage.py b/src/part2/storage.py
index b63d5fc7..b41efe15 100644
--- a/src/part2/storage.py
+++ b/src/part2/storage.py
@@ -24,11 +24,13 @@
 
 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
+FIELDS_NAME_INDEX: Final = 0
+FIELDS_PRICE_INDEX: Final = 1
+FIELDS_QUANTITY_INDEX: Final = 2
+
+PRODUCT_ID_MIN: Final[int] = 1
diff --git a/src/part2/utils.py b/src/part2/utils.py
index 11bd7a76..6fbf19f7 100644
--- a/src/part2/utils.py
+++ b/src/part2/utils.py
@@ -6,13 +6,12 @@
 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:
@@ -25,5 +24,4 @@ def normalize_price(price: Decimal) -> Decimal:
         ``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..fc9ad784 100644
--- a/src/part3/crud.py
+++ b/src/part3/crud.py
@@ -20,13 +20,13 @@
 
 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:
@@ -40,8 +40,10 @@ def generate_product_id(storage: list[Product]) -> int:
         :data:`~src.part3.storage.PRODUCT_ID_MIN` when ``storage`` is
         empty.
     """
-    # TODO: реализуйте функцию (используйте своё решение части 2)
-    return 0
+    if not storage:
+        return PRODUCT_ID_MIN
+
+    return max(product[PRODUCT_ID_INDEX] for product in storage) + 1
 
 
 def create_product(
@@ -64,8 +66,21 @@ def create_product(
         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 not name:
+        print("product name must not be blank")
+        return None
+
+    for product in storage:
+        if product[NAME_INDEX] == name:
+            print(f"product name '{name}' is already taken")
+            return None
+
+    product_id = generate_product_id(storage)
+    storage.append((product_id, name, normalize_price(price), quantity))
+    return product_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -80,8 +95,12 @@ def read_product(storage: list[Product], product_id: int) -> Product | None:
         ``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
+
+    print(f"no product with id {product_id}")
+    return None
 
 
 def update_product(
@@ -110,8 +129,25 @@ def update_product(
         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 not name:
+        print("product name must not be blank")
+        return None
+
+    existing_product = read_product(storage, product_id)
+    if existing_product is None:
+        return None
+
+    for product in storage:
+        if product[NAME_INDEX] == name and product[PRODUCT_ID_INDEX] != product_id:
+            print(f"product name '{name}' is already taken")
+            return None
+
+    product = (product_id, name, normalize_price(price), quantity)
+    storage[storage.index(existing_product)] = product
+    return product
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
@@ -127,5 +163,9 @@ def delete_product(storage: list[Product], product_id: int) -> int | None:
         product carried that identifier (``storage`` is left unchanged and
         a message is printed).
     """
-    # TODO: реализуйте функцию (используйте своё решение части 2)
-    return 0
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+
+    storage.remove(product)
+    return product_id
diff --git a/src/part3/run_admin.py b/src/part3/run_admin.py
index c5feeb0b..5b0bcf68 100644
--- a/src/part3/run_admin.py
+++ b/src/part3/run_admin.py
@@ -29,22 +29,32 @@
 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:
@@ -54,7 +64,7 @@ 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
+    print(HELP_TEXT)
 
 
 def print_result(result: object) -> None:
@@ -65,7 +75,8 @@ def print_result(result: object) -> None:
             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:
@@ -88,8 +99,48 @@ def run_command(storage: list[Product], line: str) -> bool:
         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()
+            return True
+
+        case ["exit"]:
+            return False
+
+        case ["show"]:
+            print_result(get_storage_str_representation(storage))
+            return True
+
+        case ["read", id]:
+            print_result(read_product(storage, int(id)))
+            return True
+
+        case ["delete", id]:
+            print_result(delete_product(storage, int(id)))
+            return True
+
+        case ["create", *name, price, quantity]:
+            if not name:
+                print(f"'{line}' is not a command")
+                return True
+
+            fields = (" ".join(name), Decimal(price), int(quantity))
+            print_result(create_product(storage, fields))
+            return True
+
+        case ["update", id, *name, price, quantity]:
+            if not name:
+                print(f"'{line}' is not a command")
+                return True
+
+            fields = (" ".join(name), Decimal(price), int(quantity))
+            print_result(update_product(storage, int(id), fields))
+            return True
+
+        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..b41efe15 100644
--- a/src/part3/storage.py
+++ b/src/part3/storage.py
@@ -6,11 +6,11 @@
 where:
 
 * ``product_id`` -- unique positive integer key, assigned by the create
-  operation in :mod:`src.part3.crud`;
+  operation in :mod:`src.part2.crud`;
 * ``name`` -- human-readable product name, unique across the store;
 * ``price`` -- price of a single unit, held as a :class:`~decimal.Decimal`
   amount rounded to a fixed number of decimal places (see
-  :func:`src.part3.utils.normalize_price`) so that money is never
+  :func:`src.part2.utils.normalize_price`) so that money is never
   subject to binary floating-point error;
 * ``quantity`` -- number of units currently in stock.
 
@@ -24,12 +24,13 @@
 
 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
+FIELDS_NAME_INDEX: Final = 0
+FIELDS_PRICE_INDEX: Final = 1
+FIELDS_QUANTITY_INDEX: Final = 2
+
+PRODUCT_ID_MIN: Final[int] = 1
diff --git a/src/part3/utils.py b/src/part3/utils.py
index 318ded0b..3a1d943e 100644
--- a/src/part3/utils.py
+++ b/src/part3/utils.py
@@ -18,7 +18,7 @@
   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
@@ -26,16 +26,13 @@
 
 # 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:
@@ -48,8 +45,7 @@ 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 2)
-    return Decimal(0)
+    return price.quantize(PRICE_STEP, ROUND_HALF_UP)
 
 
 def normalize_product_name(name: str) -> str:
@@ -66,11 +62,18 @@ def normalize_product_name(name: str) -> str:
         The result is an empty string when ``name`` holds nothing but
         whitespace.
     """
-    # TODO: реализуйте функцию
-    return ""
+    name_words = name.split()
+    normalized_name = " ".join(name_words).lower()
 
+    return normalized_name
 
-# TODO: при необходимости добавьте свои вспомогательные функции
+
+def get_separator_str(storage_lengths: tuple[int, ...]) -> str:
+    separator = "|"
+    for length in storage_lengths:
+        separator += "-" + "-" * length + "-|"
+    separator += "\n"
+    return separator
 
 
 def get_storage_str_representation(storage: list[Product]) -> str:
@@ -91,5 +94,37 @@ def get_storage_str_representation(storage: list[Product]) -> str:
         is empty only the header and separator rows are returned, sized to
         the header labels.
     """
-    # TODO: реализуйте функцию
-    return ""
+    storage_lengths = []
+    for i in range(len(TABLE_HEADERS)):
+        max_value_length = 0
+        for elem in storage:
+            max_value_length = max(len(str(elem[i])), max_value_length)
+        storage_lengths.append(max(len(str(TABLE_HEADERS[i])), max_value_length))
+
+    table = ""
+
+    table += "|"
+    for i in range(len(TABLE_HEADERS)):
+        table += " "
+        table += str(TABLE_HEADERS[i]) + " " * (
+            storage_lengths[i] - len(str(TABLE_HEADERS[i]))
+        )
+        table += " |"
+    table += "\n"
+
+    table += get_separator_str(tuple(storage_lengths))
+
+    for product in storage:
+        row = "|"
+        for i in range(len(TABLE_HEADERS)):
+            row += (
+                " "
+                + str(product[i])
+                + " " * (storage_lengths[i] - len(str(product[i])))
+                + " |"
+            )
+        table += row + "\n"
+
+    table = table[:-1]
+
+    return table
diff --git a/src/part4/cart.py b/src/part4/cart.py
index aed9bb72..694ec0c0 100644
--- a/src/part4/cart.py
+++ b/src/part4/cart.py
@@ -9,10 +9,8 @@
 an explanatory message to stdout and returns ``None``.
 """
 
-from .storage import Product
-
-
-# TODO: при необходимости добавьте свои вспомогательные функции
+from .crud import read_product
+from .storage import QUANTITY_KEY, Product
 
 
 def add_to_cart(
@@ -46,8 +44,21 @@ def add_to_cart(
         ``None`` when the product is unknown or the store cannot cover the
         request.
     """
-    # TODO: реализуйте функцию
-    return 0
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+
+    in_stock = product[QUANTITY_KEY]
+    if in_stock < quantity:
+        print(
+            f"not enough stock for product {product_id}: "
+            f"{in_stock} available, {quantity} requested"
+        )
+        return None
+
+    product[QUANTITY_KEY] = in_stock - quantity
+    cart[product_id] = cart.get(product_id, 0) + quantity
+    return cart[product_id]
 
 
 def remove_from_cart(
@@ -83,5 +94,29 @@ 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
+    in_cart = cart.get(product_id)
+
+    if in_cart is None:
+        print(f"product {product_id} is not in the cart")
+        return None
+
+    if in_cart < quantity:
+        print(
+            f"cart holds only {in_cart} unit(s) of product {product_id}, "
+            f"cannot remove {quantity}"
+        )
+        return None
+
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+
+    product[QUANTITY_KEY] += quantity
+
+    left = in_cart - quantity
+    if left == 0:
+        del cart[product_id]
+        return 0
+
+    cart[product_id] = left
+    return left
diff --git a/src/part4/crud.py b/src/part4/crud.py
index 471eff00..91484d06 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 +41,7 @@ def generate_product_id() -> str:
     Returns:
         A freshly generated UUID, stringified.
     """
-    # TODO: реализуйте функцию
-    return ""
+    return str(uuid.uuid4())
 
 
 def create_product(
@@ -73,8 +72,27 @@ def create_product(
         and ``product_names`` are left unchanged and an explanatory
         message is printed.
     """
-    # TODO: реализуйте функцию
-    return ""
+    name = normalize_product_name(fields[NAME_KEY])
+    price = fields[PRICE_KEY]
+    quantity = fields[QUANTITY_KEY]
+
+    if not name:
+        print("product name must not be blank")
+        return None
+
+    if name in product_names:
+        print(f"product name '{name}' is already taken")
+        return None
+
+    product_id = generate_product_id()
+    storage[product_id] = {
+        NAME_KEY: name,
+        PRICE_KEY: normalize_price(price),
+        QUANTITY_KEY: quantity,
+    }
+    product_names.add(name)
+
+    return product_id
 
 
 def read_product(storage: dict[str, Product], product_id: str) -> Product | None:
@@ -88,8 +106,13 @@ 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 {}
+    product = storage.get(product_id)
+
+    if product is None:
+        print(f"no product with id {product_id}")
+        return None
+
+    return product
 
 
 def update_product(
@@ -129,8 +152,34 @@ def update_product(
         and an explanatory message is printed. Renaming a product to its
         own current name is allowed.
     """
-    # TODO: реализуйте функцию
-    return {}
+    existing_product = read_product(storage, product_id)
+    if existing_product is None:
+        return None
+
+    if NAME_KEY in fields:
+        name = normalize_product_name(fields[NAME_KEY])
+
+        if not name:
+            print("product name must not be blank")
+            return None
+
+        if name != existing_product[NAME_KEY] and name in product_names:
+            print(f"product name '{name}' is already taken")
+            return None
+
+        fields[NAME_KEY] = name
+
+    if PRICE_KEY in fields:
+        fields[PRICE_KEY] = normalize_price(fields[PRICE_KEY])
+
+    old_name = existing_product[NAME_KEY]
+    existing_product.update(fields)
+
+    if existing_product[NAME_KEY] != old_name:
+        product_names.discard(old_name)
+        product_names.add(existing_product[NAME_KEY])
+
+    return existing_product
 
 
 def delete_product(
@@ -153,5 +202,10 @@ def delete_product(
         product carried that identifier (``storage`` and ``product_names``
         are left unchanged and a message is printed).
     """
-    # TODO: реализуйте функцию
-    return ""
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+
+    product_names.discard(product[NAME_KEY])
+    del storage[product_id]
+    return product_id
diff --git a/src/part4/run_admin.py b/src/part4/run_admin.py
index 2247b29b..fb6cbe73 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 typing import Final
+from decimal import Decimal, InvalidOperation
+from typing import Any, 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 +74,31 @@ 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 build_fields(name: list[str], price: str, quantity: str) -> dict[str, Any]:
+    """Build the ``fields`` dictionary for ``create`` and ``update``.
+
+    Args:
+        name: The words of the product name, joined with single spaces.
+        price: The raw price argument.
+        quantity: The raw quantity argument.
+
+    Returns:
+        A dictionary with the ``name``, ``price`` and ``quantity`` keys.
+
+    Raises:
+        ValueError: If ``quantity`` does not parse as a base-10 integer.
+        decimal.InvalidOperation: If ``price`` does not parse as a decimal
+            number.
+    """
+    return {
+        NAME_KEY: " ".join(name),
+        PRICE_KEY: Decimal(price),
+        QUANTITY_KEY: int(quantity),
+    }
 
 
 def run_command(
@@ -91,8 +125,39 @@ 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()
+            return True
+
+        case ["exit"]:
+            return False
+
+        case ["show"]:
+            print_result(get_storage_str_representation(storage))
+            return True
+
+        case ["read", product_id]:
+            print_result(read_product(storage, product_id))
+            return True
+
+        case ["delete", product_id]:
+            print_result(delete_product(storage, product_names, product_id))
+            return True
+
+        case ["create", *name, price, quantity] if name:
+            fields = build_fields(name, price, quantity)
+            print_result(create_product(storage, product_names, fields))
+            return True
+
+        case ["update", product_id, *name, price, quantity] if name:
+            fields = build_fields(name, price, quantity)
+            print_result(update_product(storage, product_names, product_id, fields))
+            return True
+
+        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..f0034782 100644
--- a/src/part4/storage.py
+++ b/src/part4/storage.py
@@ -39,7 +39,6 @@
 type Product = dict[str, Any]
 
 # 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..372fb6a7 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,
@@ -31,16 +31,16 @@
 
 # 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 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")
+
+# Number of spaces between a cell's text and the border on each side.
+CELL_PADDING: Final[int] = 1
 
 
 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:
@@ -71,11 +70,24 @@ def normalize_product_name(name: str) -> str:
         The result is an empty string when ``name`` holds nothing but
         whitespace.
     """
-    # TODO: реализуйте функцию (используйте своё решение части 3)
-    return ""
+    return " ".join(name.split()).lower()
+
+
+def format_row(cells: list[str], widths: list[int]) -> str:
+    """Render one table row, padding each cell to its column width.
 
+    Args:
+        cells: The text of each cell, left to right.
+        widths: The width of each column, left to right.
 
-# TODO: при необходимости добавьте свои вспомогательные функции
+    Returns:
+        The row as ``| a | b | c | d |`` with every cell padded on the
+        right to its column width.
+    """
+    padded_cells = [cell.ljust(width) for cell, width in zip(cells, widths)]
+    padding = " " * CELL_PADDING
+    joiner = f"{padding}|{padding}"
+    return f"|{padding}{joiner.join(padded_cells)}{padding}|"
 
 
 def get_storage_str_representation(storage: dict[str, Product]) -> str:
@@ -96,5 +108,25 @@ 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 = [
+        [
+            product_id,
+            record[NAME_KEY],
+            str(record[PRICE_KEY]),
+            str(record[QUANTITY_KEY]),
+        ]
+        for product_id, record in storage.items()
+    ]
+
+    widths = [
+        max([len(header)] + [len(row[i]) for row in rows])
+        for i, header in enumerate(TABLE_HEADERS)
+    ]
+
+    dashes = ["-" * (width + 2 * CELL_PADDING) for width in widths]
+    separator = "|" + "|".join(dashes) + "|"
+
+    lines = [format_row(list(TABLE_HEADERS), widths), separator]
+    lines.extend(format_row(row, widths) for row in rows)
+
+    return "\n".join(lines)