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


namespace ConsoleApplication2
{
	class Program
	{
		static void Main(string[] args)
		{
#if LOCAL
			Console.SetIn(new StreamReader("test18.txt"));
#endif
			var mask = Enumerable.Range(0, 32).Select(x => (uint)1 << x).Reverse().ToArray();
			Console.ReadLine();

			var original = Console.ReadLine().Split().Select(x => uint.Parse(x)).ToArray();
			var currentA = original.ToArray();
			var currentB = original.ToArray();

			uint[] candidate = new uint[0];



			foreach (var m in mask)
			{
				var currentMax = currentA.Max();

				candidate = currentA.Select(x => x ^ m).ToArray();
				var candidateMax = candidate.Max();

				if (currentMax > candidateMax)
				{
					currentA = candidate;
				}
			}

			foreach (var m in mask.Reverse())
			{
				var currentMax = currentB.Max();

				candidate = currentB.Select(x => x ^ m).ToArray();
				var candidateMax = candidate.Max();

				if (currentMax > candidateMax)
				{
					currentB = candidate;
				}

			}

			Console.WriteLine(Math.Min(currentA.Max(), currentB.Max()));
		}
	}
}