12
2
11 -1
0 2 4 6 8 10 -1
1 1 0
2 0 0
2 1 0
3 0 1
3 1 2
4 0 2
4 1 2
5 0 3
5 1 4
6 0 4
6 1 4
7 0 5
7 1 6
8 0 6
8 1 6
9 0 7
9 1 8
10 0 8
10 1 8
11 0 9
11 0 11
11 1 10
11 1 11
-1