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

Example Input: Problem: if a 1 mm thick paper is folded so that the area is halved at every fold , then what would be the thickness of the pile after 50 folds ?
Example Output: 1 billion km', 'e ) none'

Example Input: Problem: find the least number must be subtracted from 62575 so that remaining number is divisible by 99 .
Example Output: 7

Example Input: Problem: two trains of length 100 meters and 200 meters are 450 meters apart . they are moving towards each other on parallel tracks , at speeds of 90 km / h and 72 km / h . after how many seconds will the trains meet ?
Example Output:
10