using System;

public class Program

{

    public static void Main()

    {

        var numbers = new [] { 5, 1, 2, 3, 4, 3, 5, 6 };

        for (var turtleIndex = 0; turtleIndex < numbers.Length; turtleIndex++) 

        {

            var turtle = numbers[turtleIndex];

            var turtleRightIndex = turtle - 1;

            var hare = numbers[turtleRightIndex];

            if (turtleRightIndex != turtleIndex && turtle == hare)

                Console.WriteLine(turtle);

            numbers[turtleIndex] = hare;

            numbers[turtleRightIndex] = turtle;

        }

    }

}