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

void solve() {
    ll n;
    cin >> n;
    vector<ll> A(n);
    for (ll i = 0; i < n; ++i)cin >> A[i];

    vector<ll> dp((1 << n),0ll);

    for (ll bit = 0; bit < (1 << n); ++bit) {

        ll l = -1;
        for (ll i = 0; i < n; ++i) {
            if (!(bit >> i & 1)) {l = i;break;}
        }


        for (ll i = 0; i < n; ++i) {
            if (!(bit >> i & 1)) {
                ll nb = bit | (1 << l) | (1 << i);
                dp[nb] = max(dp[nb] , dp[bit]+(A[i]^A[l]));
            }
        }
    }
    cout << dp.back() << endl;
}

int main() {
    solve();
    return 0;
}