def checksum(cheknum, clen, odd_even):

return cheknum

while True:

cardnum = input("What is your card number?: ")

if(0 < len(cardnum)):

try:

temp_list = list(cardnum)

map_object = map(int, temp_list)

# print(map_object)

cnum = list(map_object)

# simply setting ctype = cnum in python instead of saving a copy of it, python will reference the ctype to point at cnums address .hence to copy we need to use cnum[:] to actually copy it!!

ctype = cnum[:]

except:

print("INVALID")

exit()

if ((len(cardnum) != 13) and (len(cardnum) != 15) and (len(cardnum) != 16)):

print("INVALID")

exit()

# variable to hold the lenght

clen = len(cnum)

if clen == 13:

# the even is to take care of alternative numbers to not include the even numbers or first and last number and truly be alternatives.

even = 1

sumchek = checksum(cnum, clen, even)

if(sum(sumchek) % 10 == 0 and ctype[0] == 4):

print("VISA")

exit()

elif clen == 15:

# the even is to take care of alternative numbers to not include the even numbers or first and last numbers and truly be alternative.

even = 1

sumchek = checksum(cnum, clen, even)

if(sum(sumchek) % 10 == 0 and ctype[0] == 3 and(ctype[1] == 4 or ctype[1] == 7)):

print("AMEX")

exit()

elif clen == 16:

# the odd is to take care of alternative numbers.

odd = 0

sumchek = checksum(cnum, clen, odd)

if(sum(sumchek) % 10 == 0 and ctype[0] == 4):

print("VISA")

exit()

elif (sum(sumchek) % 10 == 0 and ctype[0] == 5 and(ctype[1] == 1 or ctype[1] == 2 or ctype[1] == 3 or ctype[1] == 4 or ctype[1] == 5)):

print("MASTERCARD")

exit()