#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; }

constexpr long long MAX = 5100000;
constexpr long long INF = 1LL << 60;
constexpr int inf = 1 << 28;
//constexpr long long mod = 1000000007LL;
//constexpr 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);
	*/
	int n; scanf("%d", &n);
	vector<ll> a(n); for (int i = 0; i < n; i++) scanf("%lld", &a[i]);
	vector<ll> perm(n); for (int i = 0; i < n / 2; i++) perm[i] = 1;
	sort(perm.begin(), perm.end());
	ll res = 0;
	do {
		vector<ll> v1;
		vector<ll> v2;
		for (ll i = 0; i < n; i++) {
			if (perm[i]) v1.push_back(a[i]);
			else v2.push_back(a[i]);
		}
		sort(v1.begin(), v1.end());
		sort(v2.begin(), v2.end());
		do {
			ll tmp = 0;
			for (ll i = 0; i < v1.size(); i++) {
				tmp ^= (v1[i] + v2[i]);
			}
			chmax(res, tmp);
		} while (next_permutation(v2.begin(), v2.end()));
	} while (next_permutation(perm.begin(), perm.end()));
	cout << res << endl;
	return 0;
	/*
		おまじないを使ったらscanfとprintf関連注意！！！！！！！！！！！！
	*/
}