using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Text;
using static System.Console;
using static System.Math;

namespace CP
{
    class Atria
    {
        static void Main(string[] args)
        {
            int n = int.Parse(ReadLine());
            try
            {
                var ls = new List<long>();
                for (int i = 0; i < n; i++)
                {
                    ls.Add(long.Parse(ReadLine()));
                }
                var hoge = new List<long>();
                hoge.Add(ls[0] + ls[1]);
                hoge.Add(ls[2] + ls[1]);
                hoge.Add(ls[0] + ls[2]);
                hoge.Sort();
                if (hoge[0] == hoge[1])
                {
                    WriteLine(hoge[1]);
                }
                else if (hoge[1] == hoge[2])
                {
                    WriteLine(hoge[0]);
                }
                else
                {
                    WriteLine(hoge[1]);
                }
            }
            catch (Exception)
            {
                WriteLine('"' + "assert" + '"');
            }
        }
    }
}