Contribution #656

Problem: ru/2.1.21

Added 2.1.20 2.1.21 2.1.22 2.1.23

Editor: Aliaksandr Melnichenka ( @astrosander )

Time: November 23, 2023 at 08:44 PM

GitHub commit: 0d24f7ad29451411fdea0e1d0e4ade1f99851d5d

+162 -4 lines changed