# 13 digit ISBN checker

t=0

isbn=[9,7,8,1,4,4,4,1,8,2,2,6,2]  #This is a 13 digit ISBN


for i in range (0, 12,2):
        t=t+ isbn[i]
for i in range (1, 12,2):
        t=t+isbn[i]*3


remainder = t % 10
calcedCD= (10 -remainder) % 10
if isbn[12] == calcedCD:
    print("The calculated check digit matches the last digit")
else:
    print("Oh no, they don't match!")