CF13D Triangles

Little Petya likes to draw. He drew $ N $ red and $ M $ blue points on the plane in such a way that no three points lie on the same line. Now he wonders what is the number of distinct triangles with vertices in red points which do not contain any blue point inside.

The first line contains two non-negative integer numbers $ N $ and $ M $ ( $ 0

Output one integer — the number of distinct triangles with vertices in red points which do not contain any blue point inside.