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

Ex Input:
Problem: a is twice as good a workman as b and they took 6 days together to do the work b alone can do it in .

Ex Output:
18 days


Ex Input:
Problem: when positive integer n is divided by 5 , the remainder is 1 . when n is divided by 7 , the remainder is 3 . what is the smallest positive integer k such that k + n is a multiple of 40 .

Ex Output:
7


Ex Input:
Problem: in a school with 5 classes , each class has 2 students less than the previous class . how many students are there in the largest class if the total number of students at school is 105 ?

Ex Output:

25