#include <algorithm>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>

using namespace std;

typedef long long ll;

#define MOD 1000000007

int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
  }
  vector<ll> dp(1 << n);
  for (int s = 0; s < (1 << n); ++s) {
    for (int i = 0; i < n; ++i) {
      for (int j = 0; j < n; ++j) {
        if (!((1 << i) & s) && !((1 << j) & s)) {
          int t = s | (1 << i) | (1 << j);
          dp[t] = max(dp[t], dp[s] + (a[i] ^ a[j]));
        }
      }
    }
  }
  cout << dp[(1 << n) - 1] << endl;
  return 0;
}