Number of rectangles

The grid consists of $n\times m$ unit squares. How many different rectangles can be drawn on it?

The sides of the rectangles must be parallel to the grid lines, and each rectangle should cover an integer number of unit squares. Two rectangles of the same size are considered different if they are located in different positions on the grid.

Input

Two positive integers $n$ and $m(n,m\le 10^5)$.

Output

Print the number of different rectangles that can be drawn on the grid.

Examples