120 - ZOJ Monthly, September 2012 - D
A n * m grid as follow:
Count the number of triangles, three of whose vertice must be grid-points.
The input consists of several cases. Each case consists of two positive integers n and m (1 ≤ n, m ≤ 1000).
For each case, output the total number of triangle.
1 1 2 2
hint for 2nd case: C(9, 3) - 8 = 76
Author: WU, Yingxin