I invite you to the contest where I authored all the problems. There are tasks that couldn't make it to the Official Codeforces Round. But they are still not that bad :)
I hope you enjoy the problems. Thanks for participating!
If you have any feedback or suggestions, please feel free to leave them in the comments. Your feedback will help improve my future contests.
UPD: My apologies! The author's idea for problem D was incorrect. I hope that the solution is now correct. All the submissions for this problem were rejudged, and three samples were added.
UPD2: Problem D has been hopefully fixed. Many thanks to juliany2 for detecting and correcting the problem.