Picnic Rhombi

Time limit

Memory limit

128 MB

Problem

A group of people on a picnic divides a wide lawn into an N x M grid. The grid consists of unit squares of size 1 x 1.

You want to draw rhombi on this grid. All four vertices of a rhombus must lie on vertices of the unit squares, that is, on lattice points of the grid. Squares are included because all four of their sides have the same length.

Given N and M, find the number of different rhombi that can be drawn. Two rhombi are different if their sets of vertices differ by at least one point.

Input

The first line contains two integers N and M.

Output

Print the number of different rhombi that can be drawn.

Constraints

1 <= N, M <= 100