what do you know?

I saw your last two contests, there were simple tasks, and if there were more harder problems, could you solve them?

Not always in task A of rounds div2 was not as easy as in the last two, and their topics or tags you can find in problemset, I recommend trying to write this one.

Then, after the contest, the tasks of the round with its tags is added to the problemset, and there you can find what topics you should prepare for solving.

I think you don't need to ask about it, you can find it yourself in codeforces, best of luck to you!