Placing Game Pieces

Time limit1sMemory limit1024 MB

Summary

Given a board N cells wide and M cells tall, count the unordered pairs of cells that touch each other diagonally.

Level: Easy2 of 10
Topics: Math, Implementation
Solved: No attempts yet

Problem

The game board is $N$ cells wide and $M$ cells tall. Count the ways to place two identical game pieces on the board so that they are diagonally adjacent to each other.

The figure below shows the case $N = 3$ , $M = 2$ .

Input

The first line contains the width $N$ of the board. $(1 \le N \le 40)$

The second line contains the height $M$ of the board. $(1 \le M \le 40)$

Output

Print the number of ways to place the pieces so that the condition above is satisfied.

Hint

Every way for the first example is shown in the figure above.

In the second example, the two pieces cannot be placed diagonally adjacent to each other, so the answer is $0$ .

Examples3

Example 1
Input
```
3
2
```
Expected output
```
4
```
Example 2
Input
```
30
1
```
Expected output
```
0
```
Example 3
Input
```
13
27
```
Expected output
```
624
```