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