//#include <bits/stdc++.h>

#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cstring>
#include <complex>
#include <stack>
#include <queue>
#include <unordered_map>
#include <map>

#define INF 100000000
#define rep(i, a) for (int i = 0; i < (a); i++)
using namespace std;
int main() {
   int n;
   cin >> n;

   vector<int> a(n);
   int i, j, k;
   for(i = 0; i < n; i++){
       cin >> a[i];
   }

   int dp[1<<n];
   for(i = 0; i < (1<<n); i++){
       dp[i] = 0;
   }

   for(i = 0; i < (1<<n); i++){
       for(j = 0; j < n; j++){
           for(k = 0; k < n; k++){
               if((i>>j)%2 == 0 && (i>>k)%2 == 0){
                   int nexti = i | (1<<j) | (1<<k);
                   int nextd = dp[i] + (a[j] ^ a[k]);
                   dp[nexti] = max(dp[nexti], nextd);
               }
           }
       }
   }

   cout << dp[(1<<n)-1] << endl;
}