human
Solve in Python:
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?

Above is a 7 x 3 grid. How many possible unique paths are there?

Note: m and n will be at most 100.

Example 1:

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 -> Right -> Down
2. Right -> Down -> Right
3. Down -> Right -> Right

Example 2:

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

What is a the Python code you requested?
assistant
#Here is the Python code you requested.

class Solution:
     def uniquePaths(self, m, n):
         """
         :type m: int
         :type n: int
         :rtype: int
         """
         a = m - 1
         b = n - 1
         ret = 1
         for i in range(b):
             ret = ret * (a+b-i) / (b-i)
         return round(ret)