Given the number of vertices (or sides), n, of a planar convex polygon, return the number of ways, w, in which you can divide the polygon into triangles, such that:
1. The division is done by drawing straight lines between existing vertices.
2. The triangles are made of existing vertices.
3. Different orientations of a similar solution are counted as different solutions.
Assume that n is a positive integer greater than 2.
n = 4 (square)
w = 2 (you can draw a line between vertices 1 and 3, as well as a line between vertices 2 and 4)
n = 5 (pentagon)
w = 5