#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <stack>
#include <queue>
#include <map>
#include <unordered_map>
#include <cassert>
using namespace std;
using i64 = int64_t;
constexpr i64 mod = 1e9 + 7;
using vi = vector<i64>;
using vvi = vector<vi>;
using ii = pair<i64, i64>;
using vii = vector<ii>;

int main() {
    vi vs, as;
    int n;
    cin >> n;
    int ans = 0;
    for (int i = 0; i < n; i++) {
        int a;
        cin >> a;
        as.push_back(a);
        vs.push_back(i);
    }
    do {
        int tmp = 0;
        for (int j = 0; j < n / 2; j++) {
            tmp ^= as[vs[j]] + as[vs[j + n / 2]];
        }
        ans = max(ans, tmp);
        reverse(vs.begin() + n / 2, vs.end());
    } while (next_permutation(vs.begin(), vs.end()));
    cout << ans << endl;
}