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

#define ll long long
#define vvi vector<vector<int>>
#define vec vector
#define pq priority_queue
#define all(v) (v).begin(), (v).end()
#define uniqueV(x) sort(x.begin(), x.end()); x.erase(unique(x.begin(), x.end()), x.end());
#define rep(i, n) for (int (i) = (0); (i) < (n); ++(i))
#define repp(i, m, n) for (int (i) = (m); (i) < (n); ++(i))
#define debug(x) cerr << #x << ": " << x << endl;
#define debug2(x, y) cerr<<"("<<#x<<", "<<#y<<") = "<<"("<<x<<", "<<y<<")"<<endl;
#define debug3(x, y, z) cerr<<"("<<#x<<", "<<#y<<", "<<#z<<") = "<<"("<<x<<", "<<y<<", "<<z<<")"<<endl;
#define debugB(value, size) cerr<<#value<<": "<<bitset<size>(value) << endl;
#define line() cerr << "---------------" << endl;

const int dx[] = {1, -1, 0, 0};
const int dy[] = {0, 0, -1, 1};
const double PI = 3.14159265358979323846;

template<typename T>
void printA(vector<T> &printArray, char between = ' ') {
   int paSize = printArray.size();
   for (int i = 0; i < paSize; i++) { cerr << printArray[i] << between;}
   if (between != '\n') {cerr << endl;}
}

// ------------------------------------------------------------------------------------------

int N;
int A[20];
bool used[20];
int ans = 0;

void dfs(int cnt, int sum) {
   if (cnt == N) {
      ans = max(ans, sum);
      // line()
   }
   rep (i, N) {
      rep (j, N) {
         if (used[i] || used[j]) continue;
         if (i == j) continue;
         used[i] = used[j] = true;
         // debug2(i, j)
         dfs(cnt+2, sum + (A[i]^A[j]));
         used[i] = used[j] = false;
      }
   }
}

int main() {
   cin >> N;
   rep (i, N) {
      cin >> A[i];
   }
   fill(used, used+N, false);

   dfs(0, 0);
   cout << ans << endl;

   return 0;
}