#include<bits/stdc++.h>
using namespace std;
using ll = long long;
template<class T> using vt = vector<T>;
template<class T> using vvt = vector<vt<T>>;
template<class T> using ttt = tuple<T,T>;
using tii = tuple<int,ll>;
using vi = vector<int>;
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define pb push_back
#define mt make_tuple
#define ALL(a) (a).begin(),(a).end()
#define FST first
#define SEC second
#define DEB cerr<<"!"<<endl
#define SHOW(a,b) cerr<<(a)<<" "<<(b)<<endl
#define DIV int(1e9+7)
const int INF = (INT_MAX/2);
const ll LLINF = (LLONG_MAX/2);
const double eps = 1e-8;
//const double PI = M_PI;  
inline ll pow(ll x,ll n,ll m){ll r=1;while(n>0){if((n&1)==1)r=r*x%m;x=x*x%m;n>>=1;}return r%m;}
inline ll lcm(ll d1, ll d2){return d1 / __gcd(d1, d2) * d2;}

/*Coding Space*/
int dp[1 << 14];
int main(){
  int n; cin >> n;
  vi in(n); rep(i,n) cin >> in[i];
  rep(state, 1 << n){
    rep(i,n)for(int j = i+1; j < n; j++){
      if((state & (1 << i)) == 0 && (state & ( 1 << j )) == 0){
        //cerr << bitset<14>(state) << " " << i << " " << j << " " << (int)(state|(1 << i) | (1 << j)) << endl;
        dp[state|(1 << i) | (1 << j)] = max(dp[state|(1 << i) | (1 << j)], dp[state] + (in[i]^in[j]));
      }
    }
  }
  cout << dp[(1 << n)-1] << endl;  
}