10
0 1 | 0 1
0 2 | 0 1
0 3 | 0 1
0 4 | 0 1
1 2 | 0 1
1 3 | 0 1
1 4 | 0 1
2 3 | 0 1
2 4 | 0 1
3 4 | 0 1