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

Ex Input:
Problem: a certain debt will be paid in 65 installments from january 1 to december 31 of a certain year . each of the first 20 payments is to be $ 410 ; each of the remaining payments is to be $ 65 more than each of the first 20 payments . what is the average ( arithmetic mean ) payment that will be made on the debt for the year ?

Ex Output:
455


Ex Input:
Problem: what is the sum of the multiples of 4 between 63 and 151 inclusive ?

Ex Output:
233


Ex Input:
Problem: if n = 2 ^ 0.15 and n ^ b = 8 , b must equal

Ex Output:

20