Mathforces. Codeforces Round 1102 (Div. 2) AB. Not a tutorial.

A: https://codeforces.com/contest/2234/s... B: https://codeforces.com/contest/2234/s... my profile: https://codeforces.com/profile/mrinmo... some tags so I hope people watch this #codeforces #competitiveprogramming #cpp #dsa