Hi ,....
A Greedy Algorithm Gets AC but it is Wrong ...
for example for this Test Case The AC code says No
5 2
1 2
1 3
2 3
4 2
4 2

Hi

I think it is better to add some more test cases to run out wrong algorithms insteat of this few tests that authors say.

You are right. The problem will be investigated.

Some anti-greedy tests were added. Problem was rejudged (submits from the online contest were not rejudged).
We apologize to all authors who solved this problem using greedy algorithm and got wrong AC verdict because of weak tests.

Why submits from online contest were not rejudged? I think, it's better to rejudge all submits. But final standings from online contest must not be changed.

At current moment it is impossible (technically) to rejudge online contest without changing final standings.