case 5 failed
input:
14 35
8 8 1
8 9 6
3 9 6
2 6 11
12 12 14
2 7 7
7 8 6
3 4 6
4 4 3
13 13 14
11 12 8
12 12 1
12 12 3
5 7 9
7 8 4
6 6 10
12 13 11
14 14 13
6 9 3
5 9 11
9 13 5
6 9 10
13 14 5
10 10 4
6 11 7
13 13 7
10 14 9
13 14 3
7 8 11
6 13 10
13 14 7
10 14 1
3 7 5
3 3 8
2 5 6
expected:
14
1 2 3 4 5 6 7 8 9 10 11 12 13 14
got:
12
1 3 4 6 7 8 9 10 11 12 13 14