#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

int ret = 0;

void go(int mask, int acc, const vector<int> &a) {
  if (!mask) {
    ret = max(ret, acc);
    return;
  }
    
  int h = -1;
  REP (i, a.size()) {
    if (mask & 1<<i) {
      h = i;
      break;
    }
  }

  for (int i = 0; i < a.size(); i++) {
    if (i != h && (mask & 1<<i)) {
      go(mask ^ 1<<i ^ 1<<h, acc ^ a[i] + a[h], a);
    }
  }
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  cin >> n;
  vector<int> a(n);
  REP (i, n) cin >> a[i];
  
  go((1<<n)-1, 0, a);
  cout << ret << endl;
  
  return 0;
}