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

Input: Consider Input: Problem: a father said to his son , ` ` i was as old as you are at the present at the time of your birth ' ' . if the father ' s age is 52 years now , the son ' s age 5 years back was :

Output: d ) 21


Input: Consider Input: Problem: how many numbers between 200 and 600 are divisible by 4 , 5 and 6 ?

Output: 6


Input: Consider Input: Problem: a train speeds past a pole in 25 seconds and a platform 150 m long in 30 seconds . its length is ?


Output: 30