diff --git a/src/part1/constants.py b/src/part1/constants.py
index 9abfbba2..588fe9f8 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..85ea27f8 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -13,13 +13,16 @@
 :func:`decode_node_id` and :func:`decode_sequence_id`.
 """
 
-import time  # noqa: F401
+import time
 
 from .constants import (  # noqa: F401
     EPOCH_MS_DEFAULT,
+    NODE_ID_BITS,
     NODE_ID_DEFAULT,
     NODE_ID_MAX,
+    SEQUENCE_ID_BITS,
     SEQUENCE_ID_MAX,
+    TIMESTAMP_BITS,
     TIMESTAMP_MS_MAX,
 )
 
@@ -35,7 +38,8 @@ def read_current_millis(epoch_ms: int) -> int:
         negative if ``epoch_ms`` lies in the future.
     """
     # TODO: реализуйте функцию
-    return 0
+
+    return int(time.time() * 1000) - epoch_ms
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
@@ -51,7 +55,7 @@ def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) ->
         generated.
     """
     # TODO: реализуйте функцию
-    return 0
+    return epoch_ms + (snowflake_id >> (NODE_ID_BITS + SEQUENCE_ID_BITS))
 
 
 def decode_node_id(snowflake_id: int) -> int:
@@ -65,7 +69,7 @@ def decode_node_id(snowflake_id: int) -> int:
         ``[0, NODE_ID_MAX]``.
     """
     # TODO: реализуйте функцию
-    return 0
+    return (snowflake_id >> SEQUENCE_ID_BITS) & NODE_ID_MAX
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
@@ -79,7 +83,7 @@ def decode_sequence_id(snowflake_id: int) -> int:
         the range ``[0, SEQUENCE_ID_MAX]``.
     """
     # TODO: реализуйте функцию
-    return 0
+    return snowflake_id & SEQUENCE_ID_MAX
 
 
 def generate_snowflake_id(
@@ -111,4 +115,18 @@ def generate_snowflake_id(
         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}], you have {node_id}")
+        return None
+    if not (0 <= sequence_id <= SEQUENCE_ID_MAX):
+        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], you have {sequence_id}")
+        return None
+    time_ms = read_current_millis(epoch_ms)
+    if time_ms > TIMESTAMP_MS_MAX:
+        print("Timestamp overflows")
+        return None
+    return (
+        (time_ms << (NODE_ID_BITS + SEQUENCE_ID_BITS))
+        | (node_id << (SEQUENCE_ID_BITS))
+        | sequence_id
+    )
diff --git a/src/part2/cart.py b/src/part2/cart.py
index 063f9aea..f1ecaa5b 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 +24,14 @@
 
 # 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_line(cart: list[CartLine], product_id: int) -> int | None:
+    for index, line in enumerate(cart):
+        if line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return index
+    return None
 
 
 def add_to_cart(
@@ -53,8 +60,33 @@ 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 product is None:
+        return None
+
+    stock_quantity = product[QUANTITY_INDEX]
+    if stock_quantity < quantity:
+        print(
+            f"not enough stock for product {product_id}: {stock_quantity} available, {quantity} requested"
+        )
+        return None
+
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], stock_quantity - quantity),
+    )
+
+    line_index = find_line(cart, product_id)
+    if line_index is not None:
+        new_quantity = cart[line_index][LINE_QUANTITY_INDEX] + quantity
+        new_line = (product_id, new_quantity)
+        cart[line_index] = new_line
+        return new_line
+
+    new_line = (product_id, quantity)
+    cart.append(new_line)
+    return new_line
 
 
 def remove_from_cart(
@@ -86,4 +118,35 @@ def remove_from_cart(
         line for the product or holds too few units.
     """
     # TODO: реализуйте функцию
-    return (0, 0)
+
+    line_index = find_line(cart, product_id)
+    if line_index is None:
+        print(f"product {product_id} is not in the cart")
+        return None
+
+    line_quantity = cart[line_index][LINE_QUANTITY_INDEX]
+    if line_quantity < quantity:
+        print(
+            f"cart holds only {line_quantity} unit(s) of product {product_id}, cannot remove {quantity}"
+        )
+        return None
+
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+
+    stock_quantity = product[QUANTITY_INDEX]
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], stock_quantity + quantity),
+    )
+
+    new_quantity = cart[line_index][LINE_QUANTITY_INDEX] - quantity
+    if new_quantity == 0:
+        del cart[line_index]
+        return (product_id, 0)
+
+    new_line = (product_id, new_quantity)
+    cart[line_index] = new_line
+    return new_line
diff --git a/src/part2/crud.py b/src/part2/crud.py
index d026cbcb..1c8cfe23 100644
--- a/src/part2/crud.py
+++ b/src/part2/crud.py
@@ -14,13 +14,13 @@
 
 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  # noqa: F401
+from .utils import normalize_price
 
 
 def generate_product_id(storage: list[Product]) -> int:
@@ -34,8 +34,9 @@ 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 +57,18 @@ def create_product(
         ``storage`` is left unchanged and a message naming the clashing
         name is printed.
     """
-    # TODO: реализуйте функцию
-    return 0
+    name, price, quantity = fields
+    for product in storage:
+        if product[NAME_INDEX] == name:
+            print(f"product name {name} is already taken")
+            return None
+
+    new_product_id = generate_product_id(storage)
+    normalized_price = normalize_price(price)
+
+    new_product = (new_product_id, name, normalized_price, quantity)
+    storage.append(new_product)
+    return new_product_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -72,8 +83,11 @@ 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(
@@ -94,13 +108,21 @@ def update_product(
             ``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)
+    name, price, quantity = fields
+    for index, product in enumerate(storage):
+        if product[PRODUCT_ID_INDEX] == product_id:
+            normalized_price = normalize_price(price)
+            updated_product = (product_id, name, normalized_price, quantity)
+            storage[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:
@@ -116,5 +138,10 @@ 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 product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            storage.remove(product)
+            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..e4bceff1 100644
--- a/src/part2/storage.py
+++ b/src/part2/storage.py
@@ -24,11 +24,9 @@
 
 type Product = tuple[int, str, Decimal, int]
 
-# TODO: задайте позиции полей внутри кортежа Product
 PRODUCT_ID_INDEX: Final = 0
-NAME_INDEX: Final = 0
-PRICE_INDEX: Final = 0
-QUANTITY_INDEX: Final = 0
+NAME_INDEX: Final = 1
+PRICE_INDEX: Final = 2
+QUANTITY_INDEX: Final = 3
 
-# TODO: задайте идентификатор первого товара в пустом хранилище
-PRODUCT_ID_MIN: Final[int] = 0
+PRODUCT_ID_MIN: Final[int] = 1
diff --git a/src/part2/utils.py b/src/part2/utils.py
index 11bd7a76..b10a471e 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 Decimal(price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP))
diff --git a/src/part3/crud.py b/src/part3/crud.py
index 68811d7e..a33034d0 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:
@@ -37,11 +37,12 @@ def generate_product_id(storage: list[Product]) -> int:
 
     Returns:
         One past the greatest identifier currently held in ``storage``, or
-        :data:`~src.part3.storage.PRODUCT_ID_MIN` when ``storage`` is
+        :data:`~src.part2.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 +65,22 @@ 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
+
+    normalized_name = normalize_product_name(fields[0])
+    if not normalized_name:
+        print("product name must not be blank")
+        return None
+    for product in storage:
+        if product[NAME_INDEX] == normalized_name:
+            print(f"product name {normalized_name} is already taken")
+            return None
+
+    new_product_id = generate_product_id(storage)
+    normalized_price = normalize_price(fields[1])
+    quantity = fields[2]
+
+    storage.append((new_product_id, normalized_name, normalized_price, quantity))
+    return new_product_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -80,8 +95,11 @@ 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 +128,30 @@ 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)
+    normalized_name = normalize_product_name(fields[0])
+
+    if not normalized_name:
+        print("product name must not be blank")
+        return None
+    target_index = -1
+    for i, item in enumerate(storage):
+        if item[PRODUCT_ID_INDEX] == product_id:
+            target_index = i
+        elif item[NAME_INDEX] == normalized_name:
+            print(f"product name {normalized_name} is already taken")
+            return None
+
+    if target_index == -1:
+        print(f"no product with id {product_id}")
+        return None
+
+    normalized_price = normalize_price(fields[1])
+    quantity = fields[2]
+
+    updated_product = (product_id, normalized_name, normalized_price, quantity)
+    storage[target_index] = updated_product
+
+    return updated_product
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
@@ -127,5 +167,10 @@ 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 (используйте своё решение части 2)
-    return 0
+
+    for product in storage:
+        if product[PRODUCT_ID_INDEX] == product_id:
+            storage.remove(product)
+            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..eb335c1a 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 +99,47 @@ 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
+    words = line.split()
+
+    if not words:
+        print(f"{line!r} is not a command")
+        return True
+
+    command = words[0]
+    args = words[1:]
+    args_count = len(args)
+
+    if command == "help" and args_count == 0:
+        show_help()
+    elif command == "exit" and args_count == 0:
+        return False
+    elif command == "show" and args_count == 0:
+        print(get_storage_str_representation(storage))
+    elif command == "create" and args_count >= 3:
+        name = " ".join(args[:-2])
+        price = Decimal(args[-2])
+        quantity = int(args[-1])
+        print_result(create_product(storage, (name, price, quantity)))
+
+    elif command == "read" and args_count == 1:
+        product_id = int(args[0])
+        print_result(read_product(storage, product_id))
+
+    elif command == "update" and args_count >= 4:
+        product_id = int(args[0])
+        name = " ".join(args[1:-2])
+        price = Decimal(args[-2])
+        quantity = int(args[-1])
+        print_result(update_product(storage, product_id, (name, price, quantity)))
+
+    elif command == "delete" and args_count == 1:
+        product_id = int(args[0])
+        print_result(delete_product(storage, product_id))
+
+    else:
+        print(f"{line!r} is not a command")
+
+    return True
 
 
 def main() -> None:
@@ -103,13 +153,13 @@ def main() -> None:
     ``exit`` ends it.
     """
     storage: list[Product] = []
-    running = True
+    is_running = True
 
-    while running:
+    while is_running:
         line = input(PROMPT).strip()
 
         try:
-            running = run_command(storage, line)
+            is_running = run_command(storage, line)
 
         except (ValueError, InvalidOperation):
             print(f"{line!r} names a command but its arguments are invalid")
diff --git a/src/part3/storage.py b/src/part3/storage.py
index c5e34be5..36e9af7f 100644
--- a/src/part3/storage.py
+++ b/src/part3/storage.py
@@ -27,9 +27,9 @@
 # TODO: задайте позиции полей внутри кортежа Product (используйте своё решение
 # части 2)
 PRODUCT_ID_INDEX: Final = 0
-NAME_INDEX: Final = 0
-PRICE_INDEX: Final = 0
-QUANTITY_INDEX: Final = 0
+NAME_INDEX: Final = 1
+PRICE_INDEX: Final = 2
+QUANTITY_INDEX: Final = 3
 
 # TODO: задайте идентификатор первого товара в пустом хранилище
-PRODUCT_ID_MIN: Final[int] = 0
+PRODUCT_ID_MIN: Final[int] = 1
diff --git a/src/part3/utils.py b/src/part3/utils.py
index 318ded0b..735e20ad 100644
--- a/src/part3/utils.py
+++ b/src/part3/utils.py
@@ -18,24 +18,24 @@
   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:
@@ -49,7 +49,7 @@ def normalize_price(price: Decimal) -> Decimal:
         with halves rounded up.
     """
     # TODO: реализуйте функцию (используйте своё решение части 2)
-    return Decimal(0)
+    return price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP)
 
 
 def normalize_product_name(name: str) -> str:
@@ -67,10 +67,7 @@ def normalize_product_name(name: str) -> str:
         whitespace.
     """
     # TODO: реализуйте функцию
-    return ""
-
-
-# TODO: при необходимости добавьте свои вспомогательные функции
+    return " ".join(name.split()).lower()
 
 
 def get_storage_str_representation(storage: list[Product]) -> str:
@@ -92,4 +89,34 @@ def get_storage_str_representation(storage: list[Product]) -> str:
         the header labels.
     """
     # TODO: реализуйте функцию
-    return ""
+
+    rows = []
+
+    for product in storage:
+        rows.append(
+            [
+                str(product[PRODUCT_ID_INDEX]),
+                str(product[NAME_INDEX]),
+                str(product[PRICE_INDEX]),
+                str(product[QUANTITY_INDEX]),
+            ]
+        )
+    widths = [len(header) for header in TABLE_HEADERS]
+    for row in rows:
+        for index, cell in enumerate(row):
+            widths[index] = max(widths[index], len(cell))
+
+    lines = []
+    header_cells = [
+        f" {header:<{widths[index]}} " for index, header in enumerate(TABLE_HEADERS)
+    ]
+    lines.append("|" + "|".join(header_cells) + "|")
+
+    separator = ["-" * (column_width + 2) for column_width in widths]
+    lines.append("|" + "|".join(separator) + "|")
+
+    for row in rows:
+        cells = [f" {cell:<{widths[index]}} " for index, cell in enumerate(row)]
+        lines.append("|" + "|".join(cells) + "|")
+
+    return "\n".join(lines)
diff --git a/src/part4/cart.py b/src/part4/cart.py
index aed9bb72..13aa27e2 100644
--- a/src/part4/cart.py
+++ b/src/part4/cart.py
@@ -9,7 +9,7 @@
 an explanatory message to stdout and returns ``None``.
 """
 
-from .storage import Product
+from .storage import QUANTITY_KEY, Product
 
 
 # TODO: при необходимости добавьте свои вспомогательные функции
@@ -46,8 +46,24 @@ def add_to_cart(
         ``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
+
+    product = storage[product_id]
+
+    if product[QUANTITY_KEY] < quantity:
+        print(
+            f"not enough stock for product {product_id}: "
+            f"{product[QUANTITY_KEY]} available, {quantity} requested"
+        )
+        return None
+
+    product[QUANTITY_KEY] -= quantity
+    cart[product_id] = cart.get(product_id, 0) + quantity
+
+    return cart[product_id]
 
 
 def remove_from_cart(
@@ -83,5 +99,27 @@ def remove_from_cart(
         (zero means the product was dropped from the cart), or ``None`` when
         the cart does not hold the product or holds too few units.
     """
-    # TODO: реализуйте функцию
-    return 0
+
+    if product_id not in cart:
+        print(f"product {product_id} is not in the cart")
+        return None
+
+    if cart[product_id] < quantity:
+        print(
+            f"cart holds only {cart[product_id]} unit(s) of product {product_id}, "
+            f"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..a624055d 100644
--- a/src/part4/crud.py
+++ b/src/part4/crud.py
@@ -23,16 +23,16 @@
 than a scan over ``storage.values()``.
 """
 
-import uuid  # noqa: F401
+import uuid
 from typing import Any
 
-from .storage import (  # noqa: F401
+from .storage import (
     NAME_KEY,
     PRICE_KEY,
     QUANTITY_KEY,
     Product,
 )
-from .utils import normalize_price, normalize_product_name  # noqa: F401
+from .utils import normalize_price, normalize_product_name
 
 
 def generate_product_id() -> str:
@@ -41,8 +41,8 @@ def generate_product_id() -> str:
     Returns:
         A freshly generated UUID, stringified.
     """
-    # TODO: реализуйте функцию
-    return ""
+
+    return str(uuid.uuid4())
 
 
 def create_product(
@@ -73,8 +73,31 @@ def create_product(
         and ``product_names`` are left unchanged and an explanatory
         message is printed.
     """
-    # TODO: реализуйте функцию
-    return ""
+
+    raw_name = fields[NAME_KEY]
+    normalized_name = normalize_product_name(raw_name)
+
+    if not normalized_name:
+        print("product name must not be blank")
+        return None
+
+    if normalized_name in product_names:
+        print(f"product name '{normalized_name}' is already taken")
+        return None
+
+    product_id = generate_product_id()
+    normalized_price = normalize_price(fields[PRICE_KEY])
+
+    product_record: Product = {
+        NAME_KEY: normalized_name,
+        PRICE_KEY: normalized_price,
+        QUANTITY_KEY: fields[QUANTITY_KEY],
+    }
+
+    storage[product_id] = product_record
+    product_names.add(normalized_name)
+
+    return product_id
 
 
 def read_product(storage: dict[str, Product], product_id: str) -> Product | None:
@@ -88,8 +111,11 @@ def read_product(storage: dict[str, Product], product_id: str) -> Product | None
         The matching product record, or ``None`` when no product carries
         that identifier (a message is printed in that case).
     """
-    # TODO: реализуйте функцию
-    return {}
+
+    if product_id not in storage:
+        print(f"no product with id {product_id}")
+        return None
+    return storage[product_id]
 
 
 def update_product(
@@ -129,8 +155,42 @@ def update_product(
         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]
+
+    if NAME_KEY in fields:
+        raw_name = fields[NAME_KEY]
+        normalized_name = normalize_product_name(raw_name)
+
+        if not normalized_name:
+            print("product name must not be blank")
+            return None
+
+        current_name = product[NAME_KEY]
+        if normalized_name != current_name and normalized_name in product_names:
+            print(f"product name '{normalized_name}' is already taken")
+            return None
+
+        fields[NAME_KEY] = normalized_name
+
+    if PRICE_KEY in fields:
+        fields[PRICE_KEY] = normalize_price(fields[PRICE_KEY])
+
+    old_name = product[NAME_KEY]
+
+    for key, value in fields.items():
+        product[key] = value
+
+    new_name = product[NAME_KEY]
+    if old_name != new_name:
+        product_names.remove(old_name)
+        product_names.add(new_name)
+
+    return product
 
 
 def delete_product(
@@ -153,5 +213,11 @@ def delete_product(
         product carried that identifier (``storage`` and ``product_names``
         are left unchanged and a message is printed).
     """
-    # TODO: реализуйте функцию
-    return ""
+
+    if product_id not in storage:
+        print(f"no product with id {product_id}")
+        return None
+
+    product = storage.pop(product_id)
+    product_names.remove(product[NAME_KEY])
+    return product_id
diff --git a/src/part4/run_admin.py b/src/part4/run_admin.py
index 2247b29b..75266d7c 100644
--- a/src/part4/run_admin.py
+++ b/src/part4/run_admin.py
@@ -28,22 +28,33 @@
 is left untouched and the loop keeps running; only ``exit`` stops it.
 """
 
-from decimal import Decimal, InvalidOperation  # noqa: F401
+from decimal import Decimal, InvalidOperation
 from typing import Final
 
-from .crud import (  # noqa: F401
+from .crud import (
     create_product,
     delete_product,
     read_product,
     update_product,
 )
-from .storage import NAME_KEY, PRICE_KEY, QUANTITY_KEY, Product  # noqa: F401
-from .utils import get_storage_str_representation  # noqa: F401
+from .storage import NAME_KEY, PRICE_KEY, QUANTITY_KEY, Product
+from .utils import get_storage_str_representation
 
 
 # TODO: задайте приглашение и текст справки (используйте своё решение части 3)
-PROMPT: Final[str] = ""
-HELP_TEXT: Final[str] = ""
+PROMPT: Final[str] = "admin> "
+HELP_TEXT: Final[str] = """Available commands:
+    help                                       show this message
+    exit                                       leave the console
+    show                                       print the whole store as a table
+    create <name...> <price> <quantity>        add a product, print its new id
+    read <id>                                  print the product with that id
+    update <id> <name...> <price> <quantity>   overwrite that product's fields
+    delete <id>                                remove the product with that id
+
+For create and update the price and quantity are the last two words of the
+line; everything before them is the product name, so it may contain spaces
+(for example "Gibson SG Junior") and needs no quoting."""
 
 
 def show_help() -> None:
@@ -53,7 +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 (используйте своё решение части 3)
+    print(HELP_TEXT)
 
 
 def print_result(result: object) -> None:
@@ -65,6 +76,8 @@ def print_result(result: object) -> None:
             printed in that case.
     """
     # TODO: реализуйте функцию (используйте своё решение части 3)
+    if result is not None:
+        print(result)
 
 
 def run_command(
@@ -92,7 +105,43 @@ def run_command(
             ``update`` does not parse as a decimal number.
     """
     # TODO: реализуйте функцию
-    return False
+    words = line.split()
+
+    if not words:
+        print(f"{line!r} is not a command")
+        return True
+
+    command = words[0]
+    args = words[1:]
+    args_count = len(args)
+
+    if command == "help" and args_count == 0:
+        show_help()
+    elif command == "exit" and args_count == 0:
+        return False
+    elif command == "show" and args_count == 0:
+        print(get_storage_str_representation(storage))
+    elif command == "create" and args_count >= 3:
+        name = " ".join(args[:-2])
+        price = Decimal(args[-2])
+        quantity = int(args[-1])
+        fields = {NAME_KEY: name, PRICE_KEY: price, QUANTITY_KEY: quantity}
+        print_result(create_product(storage, product_names, fields))
+    elif command == "read" and args_count == 1:
+        print_result(read_product(storage, args[0]))
+    elif command == "update" and args_count >= 4:
+        product_id = args[0]
+        name = " ".join(args[1:-2])
+        price = Decimal(args[-2])
+        quantity = int(args[-1])
+        fields = {NAME_KEY: name, PRICE_KEY: price, QUANTITY_KEY: quantity}
+        print_result(update_product(storage, product_names, product_id, fields))
+    elif command == "delete" and args_count == 1:
+        print_result(delete_product(storage, product_names, args[0]))
+    else:
+        print(f"{line!r} 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..3f261630 100644
--- a/src/part4/utils.py
+++ b/src/part4/utils.py
@@ -18,10 +18,10 @@
   the longest value it holds in that particular call.
 """
 
-from decimal import ROUND_HALF_UP, Decimal  # noqa: F401
+from decimal import ROUND_HALF_UP, Decimal
 from typing import Final
 
-from .storage import (  # noqa: F401
+from .storage import (
     NAME_KEY,
     PRICE_KEY,
     QUANTITY_KEY,
@@ -33,14 +33,14 @@
 # Quantisation step derived from PRICE_PRECISION, e.g. Decimal("0.01").
 # TODO: задайте число знаков после запятой и шаг квантования (используйте своё
 # решение части 3)
-PRICE_PRECISION: Final[int] = 0
-PRICE_STEP: Final = Decimal(0)
+PRICE_PRECISION: Final[int] = 2
+PRICE_STEP: Final = Decimal(1).scaleb(-PRICE_PRECISION)
 
 # Column headers of the table produced by get_storage_str_representation,
 # left to right. The width of each column is not fixed here -- it is
 # measured per call from the data (see the function).
 # TODO: задайте заголовки столбцов таблицы (используйте своё решение части 3)
-TABLE_HEADERS: Final[tuple[str, ...]] = ()
+TABLE_HEADERS: Final[tuple[str, ...]] = ("ID", "name", "price", "quantity")
 
 
 def normalize_price(price: Decimal) -> Decimal:
@@ -54,7 +54,7 @@ def normalize_price(price: Decimal) -> Decimal:
         with halves rounded up.
     """
     # TODO: реализуйте функцию (используйте своё решение части 3)
-    return Decimal(0)
+    return price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP)
 
 
 def normalize_product_name(name: str) -> str:
@@ -72,7 +72,7 @@ def normalize_product_name(name: str) -> str:
         whitespace.
     """
     # TODO: реализуйте функцию (используйте своё решение части 3)
-    return ""
+    return " ".join(name.split()).lower()
 
 
 # TODO: при необходимости добавьте свои вспомогательные функции
@@ -97,4 +97,32 @@ def get_storage_str_representation(storage: dict[str, Product]) -> str:
         returned, sized to the header labels.
     """
     # TODO: реализуйте функцию (используйте своё решение части 3)
-    return ""
+    rows = []
+    for product_id, product in storage.items():
+        rows.append(
+            [
+                str(product_id),
+                str(product[NAME_KEY]),
+                str(product[PRICE_KEY]),
+                str(product[QUANTITY_KEY]),
+            ]
+        )
+    widths = [len(header) for header in TABLE_HEADERS]
+    for row in rows:
+        for index, cell in enumerate(row):
+            widths[index] = max(widths[index], len(cell))
+
+    lines = []
+    header_cells = [
+        f" {header:<{widths[index]}} " for index, header in enumerate(TABLE_HEADERS)
+    ]
+    lines.append("|" + "|".join(header_cells) + "|")
+
+    separator = ["-" * (column_width + 2) for column_width in widths]
+    lines.append("|" + "|".join(separator) + "|")
+
+    for row in rows:
+        cells = [f" {cell:<{widths[index]}} " for index, cell in enumerate(row)]
+        lines.append("|" + "|".join(cells) + "|")
+
+    return "\n".join(lines)