#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define ll long long
#define REP(i, n) for (ll (i) = 0; (i) < (n); (i)++)
#define REPI(i, a, b) for (ll (i) = (a); (i) < (b); (i)++)
#define int long long
using namespace std;
using P = pair<int, int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VVVI = vector<VVI>;

int N;
VI A;

int dfs(VI& x, int acc) {
  if (x.size() == 0) { return acc; }
  int ans = -1;
  REP (i, x.size()-1) {
    VI y(x);
    int tmp = acc ^ (x[i] + x.back());
    y.erase(y.begin() + i);
    y.erase(y.end() - 1);
    ans = max(ans, dfs(y, tmp));
  }
  return ans;
}
signed main() {
  cin >> N;
  A.resize(N);
  REP (i, N) { cin >> A[i]; }
  cout << dfs(A, 0) << endl;
}