#include <bits/stdc++.h>

using namespace std;

using ll = long long;

constexpr char newl = '\n';

void solve(int cur, int mask, ll score, const vector<ll>& a, ll& ans) {
    if (cur == a.size()) {
        ans = max(ans, score);
        return;
    }
    if (mask >> cur & 1) {
        solve(cur + 1, mask, score, a, ans);
        return;
    }
    mask |= (1 << cur);
    for (int i = cur; i < a.size(); i++) {
        if (mask >> i & 1) continue;
        solve(cur + 1, (mask | (1 << i)), score ^ (a[cur] + a[i]), a, ans);
    }
}

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

    int n;
    cin >> n;

    vector<ll> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    ll ans = 0;
    solve(0, 0, 0, a, ans);
    cout << ans << newl;

    return 0;
}