A robot starts at the top-left corner of an m × n grid and wants to reach the bottom-right corner. It can only move right or down.
Return the number of different paths it can take.
Examples
Example 1
- Input
- m = 3, n = 7
- Output
- 28
Example 2
- Input
- m = 3, n = 2
- Output
- 3
- Why
- Right → Down → Down, Down → Down → Right, or Down → Right → Down.
Constraints
1 <= m, n <= 100- The answer is at most
2 * 10^9.