diff --git a/src/part1/constants.py b/src/part1/constants.py
index 9abfbba2..22c27cee 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**41 - 1
+NODE_ID_MAX: Final[int] = 2**10 - 1
+SEQUENCE_ID_MAX: Final[int] = 2**12 - 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..8c015a63 100644
--- a/src/part1/snowflake.py
+++ b/src/part1/snowflake.py
@@ -13,12 +13,17 @@
 :func:`decode_node_id` and :func:`decode_sequence_id`.
 """
 
-import time  # noqa: F401
+import time
 
-from .constants import (  # noqa: F401
+from .constants import (
+    # Epoch
     EPOCH_MS_DEFAULT,
+    # Node ID
+    NODE_ID_BITS,
     NODE_ID_DEFAULT,
     NODE_ID_MAX,
+    # Sequence ID
+    SEQUENCE_ID_BITS,
     SEQUENCE_ID_MAX,
     TIMESTAMP_MS_MAX,
 )
@@ -35,7 +40,8 @@ def read_current_millis(epoch_ms: int) -> int:
         negative if ``epoch_ms`` lies in the future.
     """
     # TODO: реализуйте функцию
-    return 0
+    a = (time.time_ns() // 1000000) - epoch_ms
+    return a
 
 
 def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) -> int:
@@ -51,7 +57,8 @@ def decode_timestamp_ms(snowflake_id: int, epoch_ms: int = EPOCH_MS_DEFAULT) ->
         generated.
     """
     # TODO: реализуйте функцию
-    return 0
+    epoch_time = snowflake_id >> (SEQUENCE_ID_BITS + NODE_ID_BITS)
+    return epoch_time + epoch_ms
 
 
 def decode_node_id(snowflake_id: int) -> int:
@@ -65,7 +72,8 @@ def decode_node_id(snowflake_id: int) -> int:
         ``[0, NODE_ID_MAX]``.
     """
     # TODO: реализуйте функцию
-    return 0
+    node_num = (snowflake_id >> SEQUENCE_ID_BITS) & NODE_ID_MAX
+    return node_num
 
 
 def decode_sequence_id(snowflake_id: int) -> int:
@@ -79,7 +87,8 @@ def decode_sequence_id(snowflake_id: int) -> int:
         the range ``[0, SEQUENCE_ID_MAX]``.
     """
     # TODO: реализуйте функцию
-    return 0
+    seq_id = snowflake_id & SEQUENCE_ID_MAX
+    return seq_id
 
 
 def generate_snowflake_id(
@@ -111,4 +120,19 @@ 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}], got {node_id}")
+        return None
+    elif not (0 <= sequence_id <= SEQUENCE_ID_MAX):
+        print(f"sequence_id must be in [0, {SEQUENCE_ID_MAX}], got {sequence_id}")
+        return None
+    a = (time.time_ns() // 1000000) - epoch_ms
+    if a > TIMESTAMP_MS_MAX:
+        print("overflows")
+        return None
+    else:
+        return (
+            (a << (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..0fac6e6b 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 +24,17 @@
 
 # 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 cart_line in cart:
+        if cart_line[LINE_PRODUCT_ID_INDEX] == product_id:
+            return cart_line
+    return None
 
 
 def add_to_cart(
@@ -54,7 +64,33 @@ def add_to_cart(
         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 = product[QUANTITY_INDEX]
+    if stock < quantity:
+        print(
+            f"not enough stock for product {product_id}: {stock} available, {quantity} requested"
+        )
+        return None
+
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], stock - quantity),
+    )
+    cart_line = find_cart_line(cart, product_id)
+
+    if cart_line is not None:
+        new_cart_line = (product_id, quantity + cart_line[LINE_QUANTITY_INDEX])
+        for i in range(len(cart)):
+            if cart[i][LINE_PRODUCT_ID_INDEX] == product_id:
+                cart[i] = new_cart_line
+        return new_cart_line
+    else:
+        new_cart_line = (product_id, quantity)
+        cart.append(new_cart_line)
+        return new_cart_line
 
 
 def remove_from_cart(
@@ -86,4 +122,33 @@ def remove_from_cart(
         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
+    stock_in_cart = cart_line[LINE_QUANTITY_INDEX]
+    if stock_in_cart < quantity:
+        print(
+            f"cart holds only {stock_in_cart} unit(s) of product {product_id}, cannot remove {quantity}"
+        )
+        return None
+    product = read_product(storage, product_id)
+    if product is None:
+        return None
+    stock_in_product = product[QUANTITY_INDEX]
+    update_product(
+        storage,
+        product_id,
+        (product[NAME_INDEX], product[PRICE_INDEX], stock_in_product + quantity),
+    )
+
+    new_cart_line = (product_id, stock_in_cart - quantity)
+    index_cart_line = cart.index(cart_line)
+
+    if (stock_in_cart - quantity) != 0:
+        cart[index_cart_line] = new_cart_line
+    else:
+        cart.pop(index_cart_line)
+
+    return new_cart_line
diff --git a/src/part2/crud.py b/src/part2/crud.py
index d026cbcb..38544578 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:
@@ -35,7 +35,9 @@ def generate_product_id(storage: list[Product]) -> int:
         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(
@@ -57,7 +59,16 @@ def create_product(
         name is printed.
     """
     # TODO: реализуйте функцию
-    return 0
+
+    name, price, quan = fields
+    n_id = generate_product_id(storage)
+
+    if any(product[NAME_INDEX] == name for product in storage):
+        print(f"product name '{name}' is already taken")
+        return None
+
+    storage.append((n_id, name, normalize_price(price), quan))
+    return n_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -73,7 +84,11 @@ def read_product(storage: list[Product], product_id: int) -> Product | None:
         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(
@@ -100,7 +115,14 @@ def update_product(
         left unchanged and a message is printed).
     """
     # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    name, price, qual = fields
+    for i, product in enumerate(storage):
+        if product[PRODUCT_ID_INDEX] == product_id:
+            update = (product_id, name, normalize_price(price), qual)
+            storage[i] = update
+            return update
+    print(f"no product with id {product_id}")
+    return None
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
@@ -117,4 +139,9 @@ def delete_product(storage: list[Product], product_id: int) -> int | None:
         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..35821c5f 100644
--- a/src/part2/storage.py
+++ b/src/part2/storage.py
@@ -26,9 +26,9 @@
 
 # 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..2b6aa266 100644
--- a/src/part2/utils.py
+++ b/src/part2/utils.py
@@ -6,13 +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:
@@ -26,4 +26,4 @@ def normalize_price(price: Decimal) -> Decimal:
         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..2472e2ef 100644
--- a/src/part3/crud.py
+++ b/src/part3/crud.py
@@ -1,32 +1,26 @@
 """Create/read/update/delete operations over the in-memory product store.
 
 Every operation takes the store -- a list of
-:data:`~src.part3.storage.Product` tuples -- as its first argument and
+:data:`~src.part2.storage.Product` tuples -- as its first argument and
 works on it in place. The failure path never raises: the operation prints
 an explanatory message to stdout and returns ``None``.
 
 The identifier of a new product is derived from the store itself
 (:func:`generate_product_id`): one past the greatest identifier in use, or
-:data:`~src.part3.storage.PRODUCT_ID_MIN` when the store is empty.
-
-Every product name that reaches the store is passed through
-:func:`~src.part3.utils.normalize_product_name` first. A name that
-normalises to an empty string is rejected -- the operation prints a
-message and changes nothing. Names are also kept unique --
-:func:`create_product` refuses a normalised name that is already taken,
-and :func:`update_product` refuses one that is already taken by another
-product.
+:data:`~src.part2.storage.PRODUCT_ID_MIN` when the store is empty.
+Product names are kept unique -- :func:`create_product` refuses a name that
+is already taken.
 """
 
 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 +31,13 @@ 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
+    # TODO: реализуйте функцию
+    if not storage:
+        return PRODUCT_ID_MIN
+    return max(product[PRODUCT_ID_INDEX] for product in storage) + 1
 
 
 def create_product(
@@ -53,19 +49,31 @@ def create_product(
         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.
+            ``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.
+        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
+
+    name1, price, quan = fields
+    name = normalize_product_name(name1)
+
+    if name == "":
+        print("product name must not be blank")
+        return None
+
+    if any(product[NAME_INDEX] == name for product in storage):
+        print(f"product name '{name}' is already taken")
+        return None
+
+    n_id = generate_product_id(storage)
+    storage.append((n_id, name, normalize_price(price), quan))
+    return n_id
 
 
 def read_product(storage: list[Product], product_id: int) -> Product | None:
@@ -80,8 +88,12 @@ 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)
+    # TODO: реализуйте функцию
+    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(
@@ -104,14 +116,37 @@ def update_product(
 
     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.
+        ``None`` when no product carries that identifier (``storage`` is
+        left unchanged and a message is printed).
     """
     # TODO: реализуйте функцию
-    return (0, "", Decimal(0), 0)
+    name1, price, qual = fields
+    name = normalize_product_name(name1)
+
+    if name == "":
+        print("product name must not be blank")
+        return None
+
+    index = None
+    for i, product in enumerate(storage):
+        if product[PRODUCT_ID_INDEX] == product_id:
+            index = i
+            break
+
+    if index is None:
+        print(f"no product with id {product_id}")
+        return None
+
+    if any(
+        product[NAME_INDEX] == name and product[PRODUCT_ID_INDEX] != product_id
+        for product in storage
+    ):
+        print(f"product name '{name}' is already taken")
+        return None
+
+    updated = (product_id, name, normalize_price(price), qual)
+    storage[index] = updated
+    return updated
 
 
 def delete_product(storage: list[Product], product_id: int) -> int | None:
@@ -127,5 +162,10 @@ 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
+    # TODO: реализуйте функцию
+    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..626a678c 100644
--- a/src/part3/run_admin.py
+++ b/src/part3/run_admin.py
@@ -29,22 +29,33 @@
 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:
@@ -55,6 +66,7 @@ def show_help() -> None:
     note on how multi-word names are parsed.
     """
     # TODO: реализуйте функцию
+    print(HELP_TEXT)
 
 
 def print_result(result: object) -> None:
@@ -66,6 +78,8 @@ def print_result(result: object) -> None:
             printed in that case.
     """
     # TODO: реализуйте функцию
+    if result is not None:
+        print(result)
 
 
 def run_command(storage: list[Product], line: str) -> bool:
@@ -89,7 +103,49 @@ def run_command(storage: list[Product], line: str) -> bool:
             ``update`` does not parse as a decimal number.
     """
     # TODO: реализуйте функцию
-    return False
+
+    if line == "exit":
+        return False
+    if line == "help":
+        show_help()
+        return True
+    if line == "show":
+        print(get_storage_str_representation(storage))
+        return True
+
+    words = line.split()
+
+    if len(words) >= 4 and words[0] == "create":
+        name = " ".join(words[1:-2])
+        price = Decimal(words[-2])
+        quantity = int(words[-1])
+        result: object = create_product(storage, (name, price, quantity))
+        print_result(result)
+        return True
+
+    if len(words) == 2 and words[0] == "read":
+        product_id = int(words[1])
+        result = read_product(storage, product_id)
+        print_result(result)
+        return True
+
+    if len(words) >= 5 and words[0] == "update":
+        product_id = int(words[1])
+        name = " ".join(words[2:-2])
+        price = Decimal(words[-2])
+        quantity = int(words[-1])
+        result = update_product(storage, product_id, (name, price, quantity))
+        print_result(result)
+        return True
+
+    if len(words) == 2 and words[0] == "delete":
+        product_id = int(words[1])
+        result = delete_product(storage, product_id)
+        print_result(result)
+        return True
+
+    print(f"{line!s} is not a command")
+    return True
 
 
 def main() -> None:
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..f2fbf0a3 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
@@ -28,14 +28,14 @@
 # Quantisation step derived from PRICE_PRECISION, e.g. Decimal("0.01").
 # TODO: задайте число знаков после запятой и шаг квантования (используйте своё
 # решение части 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 +48,8 @@ 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)
+    # TODO: реализуйте функцию
+    return price.quantize(PRICE_STEP, rounding=ROUND_HALF_UP)
 
 
 def normalize_product_name(name: str) -> str:
@@ -67,7 +67,7 @@ def normalize_product_name(name: str) -> str:
         whitespace.
     """
     # TODO: реализуйте функцию
-    return ""
+    return " ".join(name.split()).lower()
 
 
 # TODO: при необходимости добавьте свои вспомогательные функции
@@ -92,4 +92,46 @@ def get_storage_str_representation(storage: list[Product]) -> str:
         the header labels.
     """
     # TODO: реализуйте функцию
-    return ""
+    ids = []
+    names = []
+    prices = []
+    quantitys = []
+
+    for product in storage:
+        ids.append(str(product[0]))
+        names.append(product[1])
+        prices.append(str(product[2]))
+        quantitys.append(str(product[3]))
+
+    w_id = max(len(TABLE_HEADERS[0]), max((len(x) for x in ids), default=0))
+    w_name = max(len(TABLE_HEADERS[1]), max((len(x) for x in names), default=0))
+    w_pr = max(len(TABLE_HEADERS[2]), max((len(x) for x in prices), default=0))
+    w_qty = max(len(TABLE_HEADERS[3]), max((len(x) for x in quantitys), default=0))
+
+    change_str_main = (
+        f"| {TABLE_HEADERS[0].ljust(w_id)} "
+        f"| {TABLE_HEADERS[1].ljust(w_name)} "
+        f"| {TABLE_HEADERS[2].ljust(w_pr)} "
+        f"| {TABLE_HEADERS[3].ljust(w_qty)} |"
+    )
+
+    change_str_dif = (
+        f"|{'-' * (w_id + 2)}"
+        f"|{'-' * (w_name + 2)}"
+        f"|{'-' * (w_pr + 2)}"
+        f"|{'-' * (w_qty + 2)}|"
+    )
+
+    rows = []
+    for i in range(len(storage)):
+        row = (
+            f"| {ids[i].ljust(w_id)} "
+            f"| {names[i].ljust(w_name)} "
+            f"| {prices[i].ljust(w_pr)} "
+            f"| {quantitys[i].ljust(w_qty)} |"
+        )
+        rows.append(row)
+
+    res = "\n".join([change_str_main, change_str_dif, *rows])
+
+    return res
diff --git a/src/part4/cart.py b/src/part4/cart.py
index aed9bb72..22b8501a 100644
--- a/src/part4/cart.py
+++ b/src/part4/cart.py
@@ -9,7 +9,10 @@
 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
@@ -47,7 +50,24 @@ def add_to_cart(
         request.
     """
     # TODO: реализуйте функцию
-    return 0
+    if product_id not in storage:
+        print(f"no product with id {product_id}")
+        return None
+
+    storage_quantity = storage[product_id][QUANTITY_KEY]
+
+    if storage_quantity < quantity:
+        print(
+            f"not enough stock for product {product_id}: {storage_quantity} available, {quantity} requested"
+        )
+        return None
+
+    storage[product_id][QUANTITY_KEY] -= quantity
+
+    new_quan = cart.get(product_id, 0) + quantity
+    cart[product_id] = new_quan
+
+    return new_quan
 
 
 def remove_from_cart(
@@ -84,4 +104,27 @@ def remove_from_cart(
         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
+
+    cart_quantity = cart[product_id]
+    if cart_quantity < quantity:
+        print(
+            f"cart holds only {cart_quantity} 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
+
+    remaining = cart_quantity - quantity
+    if remaining == 0:
+        del cart[product_id]
+    else:
+        cart[product_id] = remaining
+
+    return remaining
diff --git a/src/part4/crud.py b/src/part4/crud.py
index 471eff00..e764275c 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:
@@ -42,7 +42,7 @@ def generate_product_id() -> str:
         A freshly generated UUID, stringified.
     """
     # TODO: реализуйте функцию
-    return ""
+    return str(uuid.uuid4())
 
 
 def create_product(
@@ -74,7 +74,26 @@ def create_product(
         message is printed.
     """
     # TODO: реализуйте функцию
-    return ""
+    norm_name = normalize_product_name(fields[NAME_KEY])
+
+    if not norm_name:
+        print("product name must not be blank")
+        return None
+    if norm_name in product_names:
+        print(f"product name '{norm_name}' is already taken")
+        return None
+
+    new_id = generate_product_id()
+
+    storage[new_id] = {
+        NAME_KEY: norm_name,
+        PRICE_KEY: normalize_price(fields[PRICE_KEY]),
+        QUANTITY_KEY: fields[QUANTITY_KEY],
+    }
+
+    product_names.add(norm_name)
+
+    return new_id
 
 
 def read_product(storage: dict[str, Product], product_id: str) -> Product | None:
@@ -89,7 +108,10 @@ def read_product(storage: dict[str, Product], product_id: str) -> Product | None
         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(
@@ -130,7 +152,34 @@ def update_product(
         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]
+    current_name = product[NAME_KEY]
+
+    if NAME_KEY in fields:
+        fields[NAME_KEY] = normalize_product_name(fields[NAME_KEY])
+        if not fields[NAME_KEY]:
+            print("product name must not be blank")
+            return None
+        if fields[NAME_KEY] != current_name and fields[NAME_KEY] in product_names:
+            print(f"product name '{fields[NAME_KEY]}' is already taken")
+            return None
+
+    if PRICE_KEY in fields:
+        fields[PRICE_KEY] = normalize_price(fields[PRICE_KEY])
+
+    if NAME_KEY in fields and fields[NAME_KEY] != current_name:
+        product_names.discard(current_name)
+        product_names.add(fields[NAME_KEY])
+
+    for key in (NAME_KEY, PRICE_KEY, QUANTITY_KEY):
+        if key in fields:
+            product[key] = fields[key]
+
+    return product
 
 
 def delete_product(
@@ -154,4 +203,11 @@ def delete_product(
         are left unchanged and a message is printed).
     """
     # TODO: реализуйте функцию
-    return ""
+    if not product_id in storage:
+        print(f"no product with id {product_id}")
+        return None
+
+    product_names.discard(storage[product_id][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..81e413b0 100644
--- a/src/part4/run_admin.py
+++ b/src/part4/run_admin.py
@@ -1,9 +1,9 @@
-"""Interactive admin console for the part4 in-memory product store.
+"""Interactive admin console for the part3 in-memory product store.
 
 Running this module starts a read-eval-print loop over a single product
 store that lives in memory for the lifetime of the process. Every line
-typed at the prompt is stripped of surrounding whitespace and matched,
-with a ``match`` statement, against the set of known commands:
+typed at the prompt is stripped of surrounding whitespace and matched
+against the set of known commands:
 
 * ``help`` -- print the list of commands and what each one does;
 * ``exit`` -- leave the loop and end the program;
@@ -19,31 +19,48 @@
 product name, so a multi-word name such as ``Gibson SG Junior`` needs no
 quoting.
 
-The four CRUD commands forward to :mod:`src.part4.crud`; whatever
+The four CRUD commands forward to :mod:`src.part3.crud`; whatever
 that call returns is printed unless it is ``None``. A line whose first
 word is not a known verb, or that carries the wrong number of arguments
 for its verb, prints an "is not a command" notice. A line that names a
-command correctly but whose price or quantity argument will not parse
-prints a distinct "arguments are invalid" notice. Either way the store
-is left untouched and the loop keeps running; only ``exit`` stops it.
+command correctly but whose id, price or quantity argument will not
+parse prints a distinct "arguments are invalid" notice. Either way the
+store 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
+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
 
-# TODO: задайте приглашение и текст справки (используйте своё решение части 3)
-PROMPT: Final[str] = ""
-HELP_TEXT: Final[str] = ""
+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 +70,8 @@ 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)
+    # TODO: реализуйте функцию
+    print(HELP_TEXT)
 
 
 def print_result(result: object) -> None:
@@ -64,7 +82,9 @@ 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)
+    # TODO: реализуйте функцию
+    if result is not None:
+        print(result)
 
 
 def run_command(
@@ -75,8 +95,6 @@ def run_command(
     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.
 
@@ -86,24 +104,70 @@ def run_command(
         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.
+        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
+
+    if line == "exit":
+        return False
+    if line == "help":
+        show_help()
+        return True
+    if line == "show":
+        print(get_storage_str_representation(storage))
+        return True
+
+    words = line.split()
+
+    if len(words) >= 4 and words[0] == "create":
+        fields = {
+            NAME_KEY: " ".join(words[1:-2]),
+            PRICE_KEY: Decimal(words[-2]),
+            QUANTITY_KEY: int(words[-1]),
+        }
+        result: object = create_product(storage, product_names, fields)
+        print_result(result)
+        return True
+
+    if len(words) == 2 and words[0] == "read":
+        product_id = words[1]
+        result = read_product(storage, product_id)
+        print_result(result)
+        return True
+
+    if len(words) >= 5 and words[0] == "update":
+        product_id = words[1]
+        fields = {
+            NAME_KEY: " ".join(words[2:-2]),
+            PRICE_KEY: Decimal(words[-2]),
+            QUANTITY_KEY: int(words[-1]),
+        }
+        result = update_product(storage, product_names, product_id, fields)
+        print_result(result)
+        return True
+
+    if len(words) == 2 and words[0] == "delete":
+        product_id = words[1]
+        result = delete_product(storage, product_names, product_id)
+        print_result(result)
+        return True
+
+    print(f"{line!s} is not a command")
+    return True
 
 
 def main() -> None:
     """Run the admin console until the ``exit`` command is entered.
 
-    A single product store, and the set of normalised names it holds, are
-    created empty and kept in memory for the whole session. Each iteration
-    reads one line from stdin, strips its surrounding whitespace and hands
-    it to :func:`run_command`. A line that names a command but whose price
-    or quantity argument does not parse is caught here and reported
-    without stopping the loop; only ``exit`` ends it.
+    A single product store is created empty and kept in memory for the
+    whole session. Each iteration reads one line from stdin, strips its
+    surrounding whitespace and hands it to :func:`run_command`. A line
+    that names a command but whose id, price or quantity argument does
+    not parse is caught here and reported without stopping the loop; only
+    ``exit`` ends it.
     """
     storage: dict[str, Product] = {}
     product_names: set[str] = set()
diff --git a/src/part4/storage.py b/src/part4/storage.py
index 9acedf07..97487635 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 = "key"
diff --git a/src/part4/utils.py b/src/part4/utils.py
index d2a940ea..645b3099 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 +97,46 @@ 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 ""
+    ids = []
+    names = []
+    prices = []
+    quantitys = []
+
+    for str_prod, product in storage.items():
+        ids.append(str(str_prod))
+        names.append(product[NAME_KEY])
+        prices.append(str(product[PRICE_KEY]))
+        quantitys.append(str(product[QUANTITY_KEY]))
+
+    w_id = max(len(TABLE_HEADERS[0]), max((len(x) for x in ids), default=0))
+    w_name = max(len(TABLE_HEADERS[1]), max((len(x) for x in names), default=0))
+    w_pr = max(len(TABLE_HEADERS[2]), max((len(x) for x in prices), default=0))
+    w_qty = max(len(TABLE_HEADERS[3]), max((len(x) for x in quantitys), default=0))
+
+    change_str_main = (
+        f"| {TABLE_HEADERS[0].ljust(w_id)} "
+        f"| {TABLE_HEADERS[1].ljust(w_name)} "
+        f"| {TABLE_HEADERS[2].ljust(w_pr)} "
+        f"| {TABLE_HEADERS[3].ljust(w_qty)} |"
+    )
+
+    change_str_dif = (
+        f"|{'-' * (w_id + 2)}"
+        f"|{'-' * (w_name + 2)}"
+        f"|{'-' * (w_pr + 2)}"
+        f"|{'-' * (w_qty + 2)}|"
+    )
+
+    rows = []
+    for i in range(len(storage)):
+        row = (
+            f"| {ids[i].ljust(w_id)} "
+            f"| {names[i].ljust(w_name)} "
+            f"| {prices[i].ljust(w_pr)} "
+            f"| {quantitys[i].ljust(w_qty)} |"
+        )
+        rows.append(row)
+
+    res = "\n".join([change_str_main, change_str_dif, *rows])
+
+    return res