ggg

using System;

class Program

{

  static void Main()

  {

    int n = int.Parse(Console.ReadLine());

    string early = Console.ReadLine();

    string[] _early = early.Split();

    int[] arrItems = Array.ConvertAll<string, int>(tokens, int.Parse);

    int xor = arrItems.Aggregate((x, y) => x ^ y);

    Console.WriteLine(xor);

  }

}