Knowing the fact that 1D Fenwick Trees can be built in linear time, I am assuming that the 2D version can be built in quadratic time. I didn't manage to find anything about this. Can you help me with some links/ideas?

Hello, everyone.

I am organizing my first contest and I would really appreciate your feedback. All the details about the contest are on the sign-up page. A rough estimate of the difficulties of the tasks would be [800-2000]. Solutions are accepted only in C++. Feel free to ask any questions in the comment section or via a private talk.

UPD1: I added java, C and python.

UPD2: Thank you for attending and congratulations to everybody! I am eager to hear your impressions.