boxes and balls in a circle
Source: Nigerian Mathematics olympiad 2021 round 2 problem 2
February 14, 2021
combinatorics
Problem Statement
boxes are arranged in a circle and are numbered In a clockwise direction. A ball is assigned a number from and is placed in one of the boxes.A round consist of the following; if the current number on the ball is , the ball is moved boxes in the clockwise direction and the number on the ball is changed to if and to if . Is it possible to choose , the initial number on the ball, and the first position of the ball in such a way that the ball gets back to the same box with the same number on it for the first time after exactly rounds