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

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<endl
#define p2(s, t) cout << (s) << " " << (t) << endl
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << endl

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    ll N;
    cin >> N;

    vector<ll> A(N);
    FOR(i, 0, N){
        cin >> A.at(i);
    }

    // battle power
    vector<ll> B(1<<N);

    FOR(i, 0, 1<<N){
        FOR(a, 0, N){
            FOR(b, a+1, N){
                // a, bの箇所はフラグ0か
                bool f0 = ((i>>a)&1)==0;
                bool f1 = ((i>>b)&1)==0;
                if(f0 && f1){
                    ll battle_power = B[i] + (A[a]^A[b]);
                    ll index = i + (1<<a) + (1<<b);
                    B[index] = max(B[index], battle_power);
                }
            }
        }
    }

    ll ans = B[(1<<N)-1];
    p(ans);
    
    return 0;
}