Unique Paths

There is a robot on an m x n grid. The robot starts at the top-left corner of the grid and wants to reach the bottom-right corner.

At any point, the robot can move only in one of two directions:

Given the two integers m and n, return the number of possible unique paths that the robot can take to reach the bottom-right corner.

Example 1

Inputm = 3, n = 7

Output28

There are 28 distinct ways to move from the top-left corner to the bottom-right corner of a 3 by 7 grid.

Example 2

Inputm = 3, n = 2

Output3

From the top-left corner, the robot must make two downward moves and one rightward move, which can be arranged in 3 unique ways.

Constraints