msd_4

0 1
0 -> 0
1 -> 1
2 -> 0
3 -> 2

1 1
0 -> 0
1 -> 1
2 -> 3
3 -> 1

2 -1
0 -> 3
1 -> 2
2 -> 0
3 -> 2

3 -1
0 -> 3
1 -> 2
2 -> 3
3 -> 1