# 0062. Unique Paths

https://leetcode.com/problems/unique-paths

## Description

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:**

![](https://assets.leetcode.com/uploads/2018/10/22/robot_maze.png)

```
**Input:** m = 3, n = 7
**Output:** 28
```

**Example 2:**

```
**Input:** m = 3, n = 2
**Output:** 3
**Explanation:**
From the top-left corner, there are a total of 3 ways to reach the bottom-right corner:
1. Right -> Down -> Down
2. Down -> Down -> Right
3. Down -> Right -> Down
```

**Example 3:**

```
**Input:** m = 7, n = 3
**Output:** 28
```

**Example 4:**

```
**Input:** m = 3, n = 3
**Output:** 6
```

**Constraints:**

* `1 <= m, n <= 100`
* It's guaranteed that the answer will be less than or equal to `2 * 109`.

## ac

```java
```
