#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

const long long MAX = 5100000;
const long long INF = 1LL << 60;
const long long mod = 1000000007LL;
//const long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;


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

	ll n; scanf("%lld", &n);
	vector<ll> a(n); for (ll i = 0; i < n; i++) scanf("%lld", &a[i]);
	vector<ll> perm1(n, 1); for (ll i = 0; i < n / 2; i++) perm1[i] = 0;
	ll res = 0;
	do {
		vector<ll> v,perm2;

		for (ll i = 0; i < n; i++) {
			if (!perm1[i]) perm2.push_back(i);
			else v.push_back(i);
		}
		do {
			ll tmp = 0;

			for (ll i = 0; i < n / 2; i++) {
				tmp ^= (a[v[i]] + a[perm2[i]]);
			}

			chmax(res, tmp);
		} while (next_permutation(perm2.begin(), perm2.end()));
	} while (next_permutation(perm1.begin(), perm1.end()));
	cout << res << endl;

	return 0;
}