Contribution #513

Problem: ru/5.2.3

Added 5.2.3 5.2.4 5.2.5 5.2.8

Editor: Aliaksandr Melnichenka ( @astrosander )

Time: November 7, 2023 at 09:49 PM

GitHub commit: 0f7890a996793725d4574b3ff2b3cb94b1ac9f9c

+259 -50 lines changed