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

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

const int MAX_N = 14;

int N, match[MAX_N];
int64 A[MAX_N];

int64 dfs(int pos)
{
    int64 res = 0;
    if (pos == N)
    {
        for (int i = 0; i < N; i++)
        {
            if (match[i] > i)
            {
                res ^= A[i] + A[match[i]];
            }
        }
        return res;
    }
    else if (match[pos] != -1)
    {
        return dfs(pos + 1);
    }

    for (int partner = pos + 1; partner < N; partner++)
    {
        if (match[partner] < 0)
        {
            match[pos] = partner;
            match[partner] = pos;
            res = max(res, dfs(pos + 1));
            match[pos] = match[partner] = -1;
        }
    }

    return res;
}

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

    cin >> N;

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

    memset(match, -1, sizeof(match));
    // O(N(N-1)!!)
    cout << dfs(0) << endl;

    return 0;
}