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

Input: Consider Input: Problem: a certain elevator has a safe weight limit of 2,000 pounds . what is the greatest possible number of people who can safely ride on the elevator at one time with the average ( arithmetic mean ) weight of half the riders being 200 pounds and the average weight of the others being 230 pounds ?

Output: 9


Input: Consider Input: Problem: how many digits are required to number a book containing 240 pages ?

Output: 612


Input: Consider Input: Problem: if a - b = 3 and a ^ 2 + b ^ 2 = 33 , find the value of ab .


Output: 12