Working on Exercise #4

When I first looked at Exercise #4, I said to myself: "Boy, that's gonna be hard". However, with pages of paper and pencil work, it didn't seem as hard as it was in the beginning. The key to solve this problem is recursion, again. Since I think this course is basicly mainly on recursion, it's beneficial for us to use recursion in everything we do. So, to solve the problem, all you have to do is dividing the big problem into smaller parts and solve it.