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

Example Input: Problem: joan took out a mortgage from hel local bank . each monthly mortgage payment she makes must be triple the amount of the previous month ' s payment . if her first payment is $ 100 , and the total amount she must pay back is $ 914800 , how many months will it take joan to pay back her mortgage ?
Example Output: 9

Example Input: Problem: 2,7 , 17,3 , 11,19 , 5,13 , __
Example Output: 23

Example Input: Problem: a company wants to spend equal amounts of money for the purchase of two types of computer printers costing $ 400 and $ 350 per unit , respectively . what is the fewest number of computer printers that the company can purchase ?
Example Output:
15