15
1: 4,5,6,7.
2: 4,5,6,7,8.
3: 5,6,7,8.
4: 6,7,8.
5: 7,8.
6: 8.
3: 1.
1: 1,2.
2: 2,3.
3: 3,4.
4: 4,5.
5: 5,6.
6: 6,7.
7: 7,8.
8: 8,1,0.
8