text: from cs50 import get_int
  from math import floor
  
  
  def main():
      digit1 = 0
      digit2 = 0
      num_digits = 0
      sum_of_double_odds = 0
      sum_of_evens = 0
      cc_number = get_int("Number: ")
  
      while cc_number > 0:
          digit2 = digit1
          digit1 = cc_number % 10
  
          if num_digits % 2 == 0:
              sum_of_evens += digit1
          else:
              multiple = 2 * digit1
              sum_of_double_odds += (multiple // 10) + (multiple % 10)
  
          cc_number //= 10
          num_digits += 1
  
      is_valid = (sum_of_evens + sum_of_double_odds) % 10 == 0
      first_two_digits = (digit1 * 10) + digit2
  
      if digit1 == 4 and num_digits >= 13 and num_digits <= 16 and is_valid:
          print("VISA\n")
      elif first_two_digits >= 51 and first_two_digits <= 55 and num_digits == 16 and is_valid:
          print("MASTERCARD\n")
      elif (first_two_digits == 34 or first_two_digits == 37) and num_digits == 15 and is_valid:
          print("AMEX\n")
      else:
          print("INVALID\n")
  
  
  if __name__ == "__main__":
      main()
  