The 13-digit International Standard Book Number (ISBN) is a unique code that identifies a book commercially. The last digit is a check digit used for error detection. To calculate its value, each digit of the first twelve digits is alternately multiplied, from left to right, by 1 or 3. The products are summed up and divided by 10. The check digit is the remainder of the division subtracted from 10. If it is 10, it becomes 0.
For example, assume that the first twelve digits are 978960931961.
(a) (9*1 + 7*3 + 8*1 + 9*3 + 6*1 + 0*3 + 9*1 + 3*3 + 1*1 + 9*3 + 6*1 + 1*3) = 126
(b) The check digit = 10 – (126 % 10) = 10 – 6 = 4
So the valid ISBN is: 9789609319614
Write a program that reads a 13-digit ISBN and checks the last digit to see if it is valid or not.
#Try 1:
Input:
9789609319614
Output:
Valid ISBN
#Try 2:
Input:
9781482214505
Output:
Valid ISBN
#Try 3:
Input:
9780132936493
Output:
Invalid ISBN