#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0, i##_len = (n); i < i##_len; i++)
#define reps(i, s, n) for(ll i = (s), i##_len = (n); i < i##_len; i++)
#define rrep(i, n) for(ll i = (n) - 1; i >= 0; i--)
#define rreps(i, e, n) for(ll i = (n) - 1; i >= (e); i--)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) ((ll)(x).size())
#define len(x) ((ll)(x).length())
#define endl "\n"

bool gb(ll bit, ll n) {
    return ((bit & (1LL << n)) != 0);
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    const ll inf = LONG_LONG_MIN / 2 - 1;
    ll n;
    cin >> n;
    vector<ll> a(n);
    rep(i, n) cin >> a[i];
    vector<ll> dp(1LL << n, inf);
    dp[0] = 0;
    rep(bit, 1LL << n) {
        rep(i, n) {
            if (gb(bit, i)) continue;
            rep(j, n) {
                if (i == j) continue;
                if (gb(bit, j)) continue;
                ll idx = bit | (1LL << i) | (1LL << j);
                dp[idx] = max(dp[idx], dp[bit] + (a[i] ^ a[j]));
            }
        }
    }
    cout << dp[(1LL << n) - 1] << endl;
    return 0;
}