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

Example Input: Problem: what is the greatest prime factor of 2 ^ 10 - 1 ?
Example Output: 3

Example Input: Problem: a clock shows the time as 10 a . m . if the minute hand gains 5 minutes every hour , how many minutes will the clock gain by 6 p . m . ?
Example Output: 40 minute

Example Input: Problem: 40 % of a number is added to 60 , the result is the same number . find the number ?
Example Output:
100