C. Counting Rectangles
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

Alice likes geometric objects, in particular rectangles. Today she drew a grid on a piece of paper, consisting of $$$n$$$ horizontal and $$$m$$$ vertical lines. Since rectangles are her favorite shapes, she wants to know the number of distinct rectangles on the grid that fulfill the following conditions:

  • the rectangle is non-degenerate
  • the sides must be either horizontal or vertical
  • the sides must lie on a grid line
Two rectangles are identical if and only if all corners between them coincide. Can you help her?
Input

A line containing two integers $$$n$$$–number of horizontal lines and $$$m$$$–number of vertical lines $$$(1\leq n, m\leq 100)$$$.

Output

Print one integer – the number of distinct rectangles which fulfill the conditions.

Example
Input
3 4
Output
18
Note

Grid consisting of 3 horizontal and 4 vertical lines.