Clever turtle

A grid of size $m\times n$ is given. A turtle is located in the bottom left corner and can only move right or up. Before reaching the top right corner, the turtle wondered: how many different ways are there to get from the starting point to the top right corner?

Although the turtle is smart, it is not yet able to calculate such a large number of possibilities on its own. Help the turtle find the answer to its question.

Input

Two positive integers $m$ and $n$ not exceeding $30$.

Output

Print the number of ways the turtle can reach the top right corner from the bottom left corner.

Examples