#include <bits/stdc++.h>
using namespace std;

signed main() {
  ios::sync_with_stdio(false);

  int N;
  cin >> N;

  vector<int> A(N);
  for (int i = 0; i < N; ++i) cin >> A[i];

  function<set<int>(int)> search = [&](int s) {
    if (s + 1 == 1 << N) return set<int>({0});
    int l = __builtin_ctz(~s);
    set<int> res;
    for (int i = 0; i < N; ++i) {
      if (~s >> i & 1) {
        if (i != l) {
          auto v = search(s | 1 << i | 1 << l);
          for (auto u : v) res.emplace(A[i] + A[l] ^ u);
        }
      }
    }
    return res;
  };

  auto v = search(0);
  cout << *v.rbegin() << endl;

  return 0;
}