OddNumber

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;

namespace _4.OddNumber
{
    class OddNumber
    {
        static void Main(string[] args)
        {
            SortedDictionary<long, bool> oddTime = new SortedDictionary<long,bool>();
            int n = int.Parse(Console.ReadLine());
            long number;
            for (int i = 0; i < n; i++)
            {
                number = long.Parse(Console.ReadLine());
                if (oddTime.ContainsKey(number))
                {
                    oddTime.Remove(number);
                }
                else
                {
                    oddTime.Add(number,true);
                }
            }
            Console.WriteLine(oddTime.Max().Key);
        }
    }
}