class Solution {
    public int uniquePaths(int m, int n) {
        int[][] dp = new int[m][n];
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (i==0 || j == 0)
                    dp[i][j] = 1;
                else
                    dp[i][j] = dp[i-1][j]+dp[i]+dp[j-1];
            }
        }
        return dp[m-1][n-1];
    }
}