def generate_ean13_checksum(ean12):
    if len(ean12) != 12:
        return None
    digits = [int(digit) for digit in ean12]
    odd_sum = sum(digits[::2])
    even_sum = sum(digits[1::2])
    total = odd_sum + 3 * even_sum
    checksum = 10 - (total % 10)
    if checksum == 10:
        checksum = 0
    return checksum


def generate_barcode(product_id: int):
    product_id = str(product_id)
    # 4 - D
    # 6 - E
    # 5 - N
    # 2 - C
    # 4652 - DENCO_C (C - CRM)
    supplier_part = 4652_5
    article_part = product_id.ljust(7, '0')
    barcode = f'{supplier_part}{article_part}'
    checksum_code = generate_ean13_checksum(barcode)
    return f'{barcode}{checksum_code}'