You can try to submit with some other compiler. Today, while I was solving a problem on CF, I got WA on test 1 and it worked perfectly fine on my computer. Then I changed the compiler from GNU C++ 11 to GNU C++ 14 and I got AC. I hope this helps :)

The best way to find out what's wrong is to use custom invocation tool it runs your code with custom input on CF server.It's better if you try to find the problem yourself because exact thing can happen during contest and there will be no way to ask someone else to help(i mean you can ask someone but that's against the rules).

I just noticed that python's set are not ordered.. sorting the elements of list has fixed the problem.

• AC sub with python 58446948
• AC sub with c++ 58435488
• run time error with PYPY3 compiler 58447121