#include <fstream>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <cstring>
#define ifs ifstream
#define ofs ofstream
#define MAX 10010
using namespace std;
ifs fin("xor_equ.in");
ofs fout("xor_equ.out");
typedef long long ll;
ll n,a[MAX],ans[MAX];
bool cmp(ll x,ll y)
{
	if(x>y)
		return true;
	return false;
}
int main()
{
	memset(a,0,sizeof(a));
	memset(ans,0,sizeof(ans));
	fin>>n;
	for(int i=1;i<=n;i++)
		fin>>a[i];
	for(int i=1;i<=n;i++)
	{
		ans[i]=a[i]^a[i+1];
	}
	sort(ans+1,ans+1+n,cmp);
	fout<<ans[1]<<endl;
	return 0;
}