msd_4

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

1 1
0 -> 1
1 -> 0
2 -> 4
3 -> 5

2 2
0 -> 1
1 -> 0
2 -> 4
3 -> 6

3 1
0 -> 7
1 -> 6
2 -> 5
3 -> 0

4 3 
0 -> 0
1 -> 1
2 -> 2
3 -> 7

5 0
0 -> 6
1 -> 7
2 -> 3
3 -> 1

6 3
0 -> 6
1 -> 7
2 -> 3
3 -> 2

7 2
0 -> 7
1 -> 6
2 -> 5
3 -> 4