2.4 DSOF 4
1 1
1-1
1
1-2
1-3 1
1-4 1
2 2
2-1
2
2-2 2
3 3
3-1
3-2 3
3
3-3 3
3-4 3
4 4
4-1
4
5 5
5-1
5
6 6
6-1
6-2 6
6
7 7
7-1
7