#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
#include <atcoder/all>
using ull = unsigned long long;
using namespace std;
using namespace atcoder;
using vst = vector<string>;
using ll = long long;
using ld = long double;
using P = pair<ll,ll>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vP = vector<P>;
#define fi first
#define se second
#define V(a) vector<a>
#define rep(i, n) for (ll i = 0; i < n; i++)
#define repp(i,k,n) for (ll i = k; i < n; i++)
#define per(i,s,e) for(ll i = s; i >= e; i--)
#define all(v) v.begin(),v.end()
#define yesno(a) a ? cout << "Yes" << '\n' : cout << "No" << '\n'
#define YESNO(a) a ? cout << "YES" << '\n' : cout << "NO" << '\n'
#define UNOmap unordered_map
#define UNOset unordered_set
#define join(G,a,b) G[a].push_back(b);G[b].push_back(a);
#define PB(a,b) a.emplace_back(b)
#define chmax(a,b) a=max(a,b)
#define chmin(a,b) a=min(a,b)

template<class... T>void in(T&... a){(cin >> ... >> a);}
template<class T, class... Ts>void out(const T& a, const Ts&... b){cout << a;((cout << ' ' <<  b), ...);cout << '\n';}
template<class T> void vin2(vector<T> &u,vector<T> &v){for(ll i = 0; i < (ll)v.size(); i++) in(u[i],v[i]);}
template<class T> void vin(vector<T> &v){for(ll i = 0; i < (ll)v.size(); i++)in(v[i]);}
template<class T> void vout(vector<T> &v){for(ll i = 0; i < (ll)v.size(); i++) cout << v[i] << ' ';cout << "\n";}


ll INF = 4611686018427387904;ll MOD =998244353; ll MOD1 =1000000007;
/* INF = 2^62 */

#define sl(...) ll __VA_ARGS__; in(__VA_ARGS__)
 
using mint = modint998244353;
using mint1 = modint1000000007;
using mintn = modint;


vl dx = {0,0,1,-1}, dy = {1,-1,0,0};
//----------------------------------------------



int main(){
  ios::sync_with_stdio(false);cin.tie(nullptr);cout<<fixed<<setprecision(15);
//==============================================
  
  ll dp[1LL << 14];
  ll N;
  in(N);
  vl A(N);
  vin(A);
  
  rep(msk,1LL << N){
    rep(a,N){
      rep(b,a){
        if(((msk >> a) &1 )or ((msk >> b)& 1)){
          continue;
        }
        chmax(dp[msk + (1 << a) + (1 << b)],dp[msk] + (A[a] ^ A[b]));
      }
    }
  }
  
 
  out(dp[(1 << N) - 1]);
}