Description

A robot is located at the top-left corner of an m × n grid. The robot can only move either down or right at any point in time.

The robot is trying to reach the bottom-right corner of the grid. How many unique paths are there?

Input format:

• Line 1: Integer m (rows)
• Line 2: Integer n (columns)

Examples

Input:
3
7

Output:
28

Input:
3
2

Output:
3

Note:

Print a single integer representing the total number of unique paths.