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

using namespace std;

using ll = long long;
using pp = pair<int,int>;
#define rep(i,n) for(int i = 0;i<n;i++)
#define printv(v) for(auto x : v) cout << x << " "; cout << "\n";    // v の要素を表示
#define printv2(v) for(auto x : v) {printv(x);cout << "\n";};

int N;
int A[14];


int main() { 
    // Input
    cin >> N;
    rep(i, N) cin >> A[i];
    vector<int> dp(1 << N,0);
    rep(i, 1<<N){
        rep(j, N) for (int k = j + 1;k < N; k++){
            if ((i >> j) & (i >> k) & 1){
                //cout << i << j << k << i-(1<<j)-(1<<k) << (A[j]^A[k]) << endl;
                //cout << dp[i] << "#" << dp[i-(1<<j)-(1<<k)] << endl;
                dp[i] = max(dp[i], dp[i-(1<<j)-(1<<k)]+(A[j]^A[k]));
                //cout << i << dp[i] << endl;
            }
        }
    }
    cout << dp[(1<<N)-1] << endl;
    //rep(i,1 << N) cout << dp[i] << endl;
    //rep(i, N) cout << A[i] << endl;
}