using System;

public class Program

{

    public static void Main()

    {

        int[] A = new int[]{9,3,9,3,9,7,9};

        int solo = 0;

        for(int x =0; x != A.Length; x++)

        {

            for( int y= 0; y!= A.Length; y++)

            {

                if(x != y)

                {

                    if (y==A.Length-1 && A[x] != A[y])

                    {

                        solo = A[x];

                    }

                    if(A[x] == A[y])

                        y=A.Length-1;

                }       

            }

        }

        Console.WriteLine(solo);

    }

}