diff --git a/.gitignore b/.gitignore
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+++ b/.gitignore
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+__pycache__/
+*.__pycache__
+.pytest_cache/
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diff --git a/shoe_store/logic/__init__.py b/shoe_store/logic/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/shoe_store/logic/product_calculator.py b/shoe_store/logic/product_calculator.py
new file mode 100644
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+++ b/shoe_store/logic/product_calculator.py
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+"""Расчет показателей товара для каталога."""
+
+from datetime import timedelta
+
+DISCOUNT_PERCENT = 25
+MANY_QUANTITY_THRESHOLD = 5
+
+
+def calculate_discounted_price(price, order_dates, calculation_date):
+    """Возвращает цену товара с учетом скидки.
+
+    Скидка 25% предоставляется, если в предыдущем календарном месяце
+    (относительно даты расчета) по товару не было заказов.
+
+    :param price: цена товара в рублях
+    :param order_dates: список дат заказов товара (datetime.date), может быть пустым
+    :param calculation_date: дата расчета (datetime.date)
+    :return: цена с учетом скидки, округленная до копеек
+    """
+    if price < 0:
+        raise ValueError("Цена не может быть отрицательной.")
+
+    current_month_start = calculation_date.replace(day=1)
+    previous_month_start = (current_month_start - timedelta(days=1)).replace(day=1)
+    has_orders_in_previous_month = any(
+        previous_month_start <= order_date < current_month_start
+        for order_date in order_dates
+    )
+
+    if has_orders_in_previous_month:
+        return price
+    return round(price * (100 - DISCOUNT_PERCENT) / 100, 2)
+
+
+def get_quantity_label(total_quantity):
+    """Возвращает «много», если пар больше пяти, иначе «мало».
+
+    :param total_quantity: количество пар суммарно по всем размерам
+    """
+    if total_quantity < 0:
+        raise ValueError("Количество не может быть отрицательным.")
+    if total_quantity > MANY_QUANTITY_THRESHOLD:
+        return "много"
+    return "мало"
diff --git a/shoe_store/tests/__init__.py b/shoe_store/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/shoe_store/tests/test_product_calculator.py b/shoe_store/tests/test_product_calculator.py
new file mode 100644
index 0000000..088de04
--- /dev/null
+++ b/shoe_store/tests/test_product_calculator.py
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+from datetime import date
+from logic.product_calculator import calculate_discounted_price, get_quantity_label
+
+
+def test_discounted_price_no_orders_in_previous_month_returns_price_with_discount():
+    price = 2000
+    order_dates = []
+    calculation_date = date(2027, 6, 15)
+
+    result = calculate_discounted_price(price, order_dates, calculation_date)
+
+    assert result == 1500
+
+
+def test_discounted_price_order_in_previous_month_returns_price_without_discount():
+    price = 2000
+    order_dates = [date(2027, 5, 10)]
+    calculation_date = date(2027, 6, 15)
+
+    result = calculate_discounted_price(price, order_dates, calculation_date)
+
+    assert result == 2000
+
+
+def test_quantity_label_five_pairs_returns_few():
+    result = get_quantity_label(5)
+
+    assert result == "мало"
+
+
+def test_quantity_label_six_pairs_returns_many():
+    result = get_quantity_label(6)
+
+    assert result == "много"
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