As the question title suggests, what specific past problems do the problems of the recent Educational Codeforces Round 147 remind you of?

I think this is of interest especially to newer contestants looking for extra practice, also maybe others as well.

Here are the problems for Educational Codeforces Round 147: https://codeforces.me/contest/1821

And here's the editorial: https://codeforces.me/blog/entry/115296