First of all, I'm really sorry for the issues the round had. We paid not enough attention to make sure everything works as intented and got punished for it. That was a lesson for us, we'll do our best to keep the future rounds as clean as possible.
The problem B had an issue with the checker, solutions have been recieving wrong verdicts. Unfortunately, neither its author, nor reviewers have noticed the bug.
Can you spot it without looking in comments?
It's been compiling with no warnings even with -Wall -Wextra -Wconversion flags. By no means that justifies our carelessness but the mistake was really unfortunate.
We really hope you enjoyed the problems nevertheless.
The contest will definitely be unrated for the participants affected by it.