+     0    1    2    3                *     0    1    2    3  

        0  0/0  1/0  2/0  3/0                 0  0/0  0/0  0/0  0/0   

        1  1/0  2/0  3/0  0/1                 1  0/0  1/0  2/0  3/0

        2  2/0  3/0  0/1  1/1                 2  0/0  2/0  0/1  2/1

        3  3/0  0/1  1/1  2/1                 3  0/0  3/0  2/1  1/2




                                 3123  *
                                  323  =
                               ---------
                                22101
                               12312
                              22101
                            ------------
                              3021321