using System; using static System.Console; using System.Linq; using System.Collections.Generic; class Program { static int NN => int.Parse(ReadLine()); static int[] NList => ReadLine().Split().Select(int.Parse).ToArray(); static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray(); static int[] NMi => ReadLine().Split().Select(c => int.Parse(c) - 1).ToArray(); static int[][] NMap(int n) => Enumerable.Repeat(0, n).Select(_ => NMi).ToArray(); static string[] SList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => ReadLine()).ToArray(); static long[] LList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => long.Parse(ReadLine())).ToArray(); public static void Main() { Solve(); } static void Solve() { var n = NN; var a = NList; var ans = 0; for (var i = 0; i < n; ++i) for (var j = i + 1; j < n; ++j) ans = Math.Max(ans, a[i] ^ a[j]); WriteLine(ans); } }