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

using int64 = long long;
using uint64 = unsigned long long;

const int MAX_N = 14;

int64 dp[1 << MAX_N];

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

    int N;
    cin >> N;

    vector<int64> A(N);
    for (int i = 0; i < N; i++)
    {
        cin >> A[i];
    }

    memset(dp, -1, sizeof(dp));
    dp[0] = 0;
    for (int mask = 0; mask < (1 << N); mask++)
    {
        for (int i = 0; i < N; i++)
        {
            for (int j = 0; j < N; j++)
            {
                if (i == j or (mask >> i) & 1 or (mask >> j) & 1)
                {
                    continue;
                }
                int nextMask = mask | (1 << i) | (1 << j);
                dp[nextMask] = max(dp[nextMask], dp[mask] + (A[i] ^ A[j]));
            }
        }
    }

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

    return 0;
}