/* -*- coding: utf-8 -*-
 *
 * 699.cc: No.699 ペアでチームを作ろう2 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 14;
const int NBITS = 1 << MAX_N;

/* typedef */

/* global variables */

int as[MAX_N];
int maxd = 0;

/* subroutines */

void rec(int i, int n, int bits, int d) {
  int bi = 1 << i;
  while (i < n && (bits & bi)) i++, bi <<= 1;
  if (i >= n) {
    if (maxd < d) maxd = d;
    return;
  }

  for (int j = i + 1, bj = 1 << (i + 1); j < n; j++, bj <<= 1)
    if (! (bits & bj))
      rec(i + 1, n, bits | bi | bj, d ^ (as[i] + as[j]));
}

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", &as[i]);
  int nbits = 1 << n;

  rec(0, n, 0, 0);
  printf("%d\n", maxd);
  return 0;
}