






"""simple docstring"""







def _a					(						_snake_case				):







      """simple docstring"""






      return credit_card_number.startswith(("""34""", """35""", """37""", """4""", """5""", """6""")				)

def _a					(						_snake_case				):







      """simple docstring"""






      UpperCAmelCase							     =			credit_card_number
      UpperCAmelCase							     =			0
      UpperCAmelCase							     =			len(lowercase__				) - 2
      for i in range(lowercase__ ,			-1 ,			-2				):
            #  double the value of every second digit
            UpperCAmelCase							     =			int(cc_number[i]				)
            digit *= 2
            # If doubling of a number results in a two digit number
            # i.e greater than 9(e.g., 6 × 2 = 12),
            # then add the digits of the product (e.g., 12: 1 + 2 = 3, 15: 1 + 5 = 6),
            # to get a single digit number.
            if digit > 9:
                  digit %= 10
                  digit += 1
            UpperCAmelCase							     =			cc_number[:i] + str(lowercase__				) + cc_number[i + 1 :]
            total += digit

      # Sum up the remaining digits
      for i in range(len(lowercase__				) - 1 ,			-1 ,			-2				):
            total += int(cc_number[i]				)

      return total % 10 == 0

def _a					(						_snake_case				):







      """simple docstring"""






      UpperCAmelCase							     =			F'''{credit_card_number} is an invalid credit card number because'''
      if not credit_card_number.isdigit():
            print(F'''{error_message} it has nonnumerical characters.'''				)
            return False

      if not 13 <= len(lowercase__				) <= 16:
            print(F'''{error_message} of its length.'''				)
            return False

      if not validate_initial_digits(lowercase__				):
            print(F'''{error_message} of its first two digits.'''				)
            return False

      if not luhn_validation(lowercase__				):
            print(F'''{error_message} it fails the Luhn check.'''				)
            return False

      print(F'''{credit_card_number} is a valid credit card number.'''				)
      return True


if __name__ == "__main__":
  import doctest

  doctest.testmod()
  validate_credit_card_number("""4111111111111111""")
  validate_credit_card_number("""32323""")





'''simple docstring'''





def snake_case_     (					lowercase__		):
  return sum(i for i in range(1   ,       number // 2 + 1		) if number % i == 0		) == number


if __name__ == "__main__":
      print("""Program to check whether a number is a Perfect number or not...""")
      SCREAMING_SNAKE_CASE     =       int(input("""Enter number: """).strip())
      print(F'{number} is {"" if perfect(number) else "not "}a Perfect Number.')



