Hi codeforces, I am realative beginner in the world of algorithms and recently I have come across the pigeon-hole principle and I am slightly overwhelmed as even though I understand the principle, I am not able to develop a thinking strategy for solving problems like this, can someone please share a tutorial so that I can develop more on thinking or a list of beginner problems for me to get started on. Thank you, any help is greatly appreciated!

Hi Codeforces, I ask as a person who wants to learn, could you give me some problems that involve greedy digit manipulation of a number, somewhat similar to this and this Any help would be appreciated. Thanks!!