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


int dfs(int used, int n_rem, int score, const vector<int>& As){
    if (n_rem == 0) return score;
    int record = score;
    for (int i = 0; i < As.size() - 1; ++i){
        if (used & (1 << i)) continue;
        for (int j = i + 1; j < As.size(); ++j){
            if (used & (1 << j)) continue;
            int new_used = used | (1 << i) | (1 << j);
            int new_score = score + (As[i] ^ As[j]);
            record = max(record, dfs(new_used, n_rem - 2, new_score, As));
        }
    }
    return record;
}


int main() {
    int N;
    cin >> N;
    vector<int> As(N);
    for (auto & a : As) cin >> a;

    cout << dfs(0, N, 0, As) << endl;

    return 0;
}