#include <iostream>
#include <vector>
#include <list>
#include <algorithm>
#include <string>
#include <sstream>
#include <stack>
#include <iomanip>
#include <numeric>
#include <queue>
#include <climits>
#include <set>
#include <complex>
#include <cmath>
#include <cstring>
#include <map>
using namespace std;
using ll = long long;
#define MOD 1000000007
#define INF 1LL << 59
using ld = long double;

int N;
int arr[15];
int maxV = 0;
vector<pair<int, int>> vp;

void dfs(int d, bool used[15], vector<int> v)
{
    if (d == N / 2)
    {
        int sum = 0;
        for (int i = 0; i < (int)v.size(); ++i)
        {
            sum = sum ^ v[i];
        }
        maxV = max(maxV, sum);
        return;
    }

    for (int i = 0; i < (int)vp.size(); ++i)
    {
        if (!used[vp[i].first] && !used[vp[i].second])
        {
            used[vp[i].first] = true;
            used[vp[i].second] = true;

            v.push_back(arr[vp[i].first] + arr[vp[i].second]);
            dfs(d + 1, used, v);
            v.pop_back();
            used[vp[i].first] = false;
            used[vp[i].second] = false;
        }
    }
}
int main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    //cout << fixed << setprecision(5);

    cin >> N;
    for (int i = 0; i < N; ++i)
        cin >> arr[i];

    for (int i = 0; i < N; ++i)
    {
        for (int j = i + 1; j < N; ++j)
        {
            vp.push_back({i, j});
        }
    }
    bool used[N];
    for (int i = 0; i < N; ++i)
        used[i] = false;
    vector<int> v;
    dfs(0, used, v);

    cout << maxV << endl;
    return 0;
}