I solved this problem using RBS (Regular Bracket Sequence) pattern. If you consider the positive numbers as the number of open brackets and the negative numbers as the number of closing brackets, you will see "If the total sequence is regular and it's closed then the answer is yes".

So you will get Yes for ( ()()() ) or ((())) or ( ( () ((())) ) ). But if the bracket is like this ()()() then it's no because in this case you can't get back to the first index.

Great contest. The problemset was amazing and so fun to solve. Enjoyed this contest so much.

What is uphack? I still got AC after being hacked in problem D. Even the rating changed. I don't understand. Someone please explain if you know something. This my submission for D

I know. But my point was if I got a correct verdict in contest time maybe I could solve the problem. But I didn't. I got the correct verdict in system testing. Why ? I am the one who suffered.

The test case was 2. It was already in the pretest. From my previous submission I can see that my answer for that case wasn't considered wrong.

NO. It's not like that. The test case existed before. The test case was -

1 0

For this I printed "0 0", it got accepted in contest time. But now I am getting WA.

I have a problem with the problem D. In contest time I got "Accepted". But now I got "wrong Answer" in the same test case (Test case 2). So, why I didn't get "WA" in contest time. I still had 10-15 minutes. Please help me with this situation.