Contribution #646

Problem: ru/2.1.12

Added 2.1.9 2.1.10 2.1.12 2.1.13 2.1.15-2.1.18

Editor: Aliaksandr Melnichenka ( @astrosander )

Time: November 19, 2023 at 08:46 PM

GitHub commit: 4f58d5cffda1b0229360ad5013306be1667979c4

+251 -51 lines changed