ASU 214 All Soviet Union MO 1975 0,1,2 on blackboard
Source:
July 5, 2019
game strategycombinatorics
Problem Statement
Several zeros, ones and twos are written on the blackboard. An anonymous clean in turn pairs of different numbers, writing, instead of cleaned, the number not equal to each. ( instead of pair instead of instead of ). Prove that if there remains one number only, it does not depend on the processing order.