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

Ex Input:
Problem: calculate the sum of first 60 natural numbers .

Ex Output:
1830


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

Ex Output:
233


Ex Input:
Problem: a train traveling at 72 kmph crosses a platform in 30 seconds and a man standing on the platform in 15 seconds . what is the length of the platform in meters ?

Ex Output:

300 meters