First of all, apologies for a rather long absence, I was a bit tired after Round #694 (Div. 1) in which I got a significant positive rating change. It is always nice to see your work paying off, but let us get back to business.
Codeforces has an excellent archive of training contests, named gyms!
But it is very well possible that you do not know about the one beginner-friendly gym that I want to cover today, and the reason is that it is only available in Russian :|
I translated the statements to English for you, and recorded a problem walkthrough, in case you ever get stuck.
We will cover more gyms from this old but gold series by Saint Petersburg State University in the future, so stay tuned!