The task is to generate the correct answer for a given math problem.

Ex Input:
Problem: how many digits are required to number a book containing 240 pages ?

Ex Output:
612

Ex Input:
Problem: find the least number must be subtracted from 105829 so that remaining no . is divisible by 21 ?

Ex Output:
10

Ex Input:
Problem: what is the remainder of ( 3682 * 3684 * 3686 ) divided by 19 ?

Ex Output:
0