#include <cassert>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <limits.h>
#include <map>
#include <queue>
#include <set>
#include <string.h>
#include <vector>

using namespace std;
typedef long long ll;

int N;
vector<ll> A;

int dfs(int cur, int mask, int val) {
  if (mask == (1 << N) - 1) {
    return val;
  }
  int value = 0;

  if (mask >> cur & 1) {
    return dfs(cur + 1, mask, val);
  }

  for (int j = cur + 1; j < N; ++j) {
    if (mask >> j & 1) continue;

    int nmask = mask | (1 << cur) | (1 << j);
    int n_val = val ^ (A[cur] + A[j]);
    int v = dfs(cur + 1, nmask, n_val);
    value = max(value, v);
  }

  return value;
}

int main() {
  cin >> N;

  for (int i = 0; i < N; ++i) {
    ll a;
    cin >> a;
    A.push_back(a);
  }

  cout << dfs(0, 0, 0) << endl;

  return 0;
}