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

Ex Input:
Problem: how many liters of a 40 % iodine solution need to be mixed with 35 liters of a 20 % iodine solution to create a 34 % iodine solution ?

Ex Output:
13


Ex Input:
Problem: if x = 1 + √ 2 , then what is the value of x 4 - 4 x 3 + 4 x 2 + 3 ?

Ex Output:
4


Ex Input:
Problem: if 45 - [ 28 - { 37 - ( 15 - * ) } ] = 54 , then * is equal to :

Ex Output:

15