One way to create a task is to learn from math. You can generate some random math statement or modify some theorems to get something new and build a new task from that. For example, there is a ...

Problem 792 A. New Bus Route: https://codeforces.com/problemset/problem/792/A Problem 801 A. Vicious Keyboard: https://codeforces.com/problemset/problem/801/A Problem ...