TOT 001 1980 Spring J1 S1 red and blue points on circumference
Source:
August 16, 2019
combinatoricsgameColoring
Problem Statement
On the circumference of a circle there are red and blue points. One may add a red point and change the colour of both its neighbours (to the other colour) or remove a red point and change the colour of both its previous neighbours. Initially there are two red points. Prove that there is no sequence of allowed operations which leads to the configuration consisting of two blue points.(K Kazarnovskiy, Moscow)