#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef pair<int,int> P;

int main(){
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i,n) cin >> a[i];
  int res = 0;
  for (int bit = 0; bit < (1 << n); bit++) {
    if (__builtin_popcount(bit) * 2 != n) continue;
    vector<int> x, y;
    for (int i = 0; i < n; i++) {
      if (bit & (1 << i)) x.emplace_back(a[i]);
      else y.emplace_back(a[i]);
    }
    sort(y.begin(), y.end());
    do {
      int tmp = 0;
      for (int i = 0; i < n/2; i++) tmp ^= x[i] + y[i];
      res = max(res, tmp);
    } while(next_permutation(y.begin(), y.end()));
  }
  cout << res << endl;
  return 0;
}