Contribution #114

Problem: ru/2.1.3

Added 2.1.1 2.1.2 2.1.3 2.2.1 2.2.2 2.2.3 2.3.1 2.3.2 2.3.3 2.4.2 2.4.3 2.5.1 2.5.2

Editor: Aliaksandr Melnichenka ( @astrosander )

Time: October 11, 2023 at 10:28 AM

+285 -74 lines changed