## 题目

A robot is located at the top-left corner of a *m x n* grid (marked ‘Start’ in the diagram below).

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 (marked ‘Finish’ in the diagram below).

How many possible unique paths are there?

Example 1:

1 | Input: m = 3, n = 2 |

Example 2:

1 | Input: m = 7, n = 3 |

**Constraints:**

`1 <= m, n <= 100`

- It’s guaranteed that the answer will be less than or equal to
`2 * 10 ^ 9`

.

## 思路

Math/DP.

## 代码

1 | class Solution(object): |