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

public class Program
{

    public void Proc()
    {
        int itemCount = int.Parse(Reader.ReadLine());
        this.Items = Reader.ReadLine().Split(' ').Select(a => int.Parse(a)).ToArray();

        int ans = GetAns(0, 0);

        Console.WriteLine(ans);

    }

    private Dictionary<int, int> dic = new Dictionary<int, int>();

    private int GetAns(int idx, int flags) {
        if(idx >= Items.Length) {
            return 0;
        }
        int key = 1 << idx;

        if(dic.ContainsKey(flags)) {
            return dic[flags];
        }

        if((key&flags)!=0) {
            int ret = GetAns(idx + 1, flags);
            dic[flags] = ret;
            return ret;
        }

        int ans = 0;
        for (int i = idx + 1; i < Items.Length; i++) {
            int subKey = 1 << i;
            if((flags&subKey)!=0) {
                continue;
            }
            int val = Items[idx] ^ Items[i];
            ans = Math.Max(ans, GetAns(idx + 1, flags + key + (1 << i)) + val);
        }
        dic[flags] = ans;
        return ans;
    }

    private int[] Items;

    public class Reader
    {
        static StringReader sr;
        public static bool IsDebug = false;
        public static string ReadLine()
        {
            if (IsDebug)
            {
                if (sr == null)
                {
                    sr = new StringReader(InputText.Trim());
                }
                return sr.ReadLine();
            }
            else
            {
                return Console.ReadLine();
            }
        }
        private static string InputText = @"



4
1 2 3 4





";
    }

    public static void Main(string[] args)
    {
#if DEBUG
        Reader.IsDebug = true;
#endif
        Program prg = new Program();
        prg.Proc();
    }
}