test 1 failed
input:
7 8
2 1
7 5
4 6
5 2
5 7
5 4
2 5
1 7
expected:
10
2 5
2 5
2 5
2 1
4 5
4 6
7 6
7 1
7 5
7 5
 got:
10
2 1
2 5
7 5
7 5
2 5
2 5
4 5
4 6
7 6
7 1