```
int uniquePaths(int m, int n)
{
vector<vector<int> > grid(m, vector<int>(n, 1));
for (int i = 1; i < m; i++)
for (int j = 1; j < n; j++)
grid[i][j] = grid[i - 1][j] + grid[i][j - 1];
return grid[m - 1][n - 1];
}
```