# 13 digit ISBN checker
evenWeight=1
oddWeight=3
t=0

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

for i in range (0, l-1,2):
        t=t+ isbn[i]*evenWeight
for i in range (1, l-1,2):
        t=t+isbn[i]*oddWeight


remainder = t % 10
calcedCD= (10 -remainder) % 10
if isbn[l-1] == calcedCD:
    print("The calculated check digit matches the last digit")
else:
    print("Oh no, they don't match!")