Please solve the programming task below using a self-contained code snippet in a markdown code block.

There is a robot on an m x n grid. The robot is initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m - 1][n - 1]). The robot can only move either down or right at any point in time.
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.
The test cases are generated so that the answer will be less than or equal to 2 * 109.
 
Please complete the following python code precisely:
```python
class Solution:
    def uniquePaths(self, m: int, n: int) -> int:
```