#include <bits/stdc++.h>

#define REP(i, n) for (int i = 0; i < (n); i++)
#define FOR(i, init, n) for (int i = init; i < (n); i++)
#define ALL(obj) (obj).begin(), (obj).end()
#define fi first
#define se second

using namespace std;
using ll = long long int;
using P = pair<int, int>;
using T = tuple<int, int, int>;
using edge = struct
{
    int to, cost;
};

const int MOD = 1e9 + 7;
const int iINF = 1e9;
const long long int llINF = 1e18;
const double PI = acos(-1.0);

const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

ll dp[1 << 16];
vector<int> A;
int N;

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

    cin >> N;
    A.resize(N);
    REP(i, N)
    {
        cin >> A[i];
    }

    REP(S, 1 << N)
    {
        REP(i, N)
        {
            if((S >> i) & 1) continue;

            FOR(j, i + 1, N)
            {
                if((S >> j) & 1) continue;

                dp[S | 1 << i | 1 << j] = max(dp[S | 1 << i | 1 << j], dp[S] + (A[i] ^ A[j]));
            }
        }
    }

    cout << dp[(1 << N) - 1] << endl;

    return 0;
}