Create problem_01

Project Euler Problem #1:

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
Find the sum of all the multiples of 3 or 5 below 1000.

My Code:
Finds the sum of all the multiples of 3 or 5 below some input N.