Kostya marks points on a circle
Source: St Petersburg 2021 9.1
December 24, 2021
combinatorics
Problem Statement
There are points on a circle. Kostya marks a point, then marks the adjacent point to the right, then he marks the point two to its right, then three to the next point's right, and so on. Which move will be the first time a point is marked twice?K. Kokhas