#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#ifdef LOCAL
#include "algo/debug.h"
#else
#define debug(...) (void(0))
#endif
void run_case();
int main() {
	std::ios_base::sync_with_stdio(false);
	std::cin.tie(nullptr);
	int T = 1;
	// cin >> T;
	while (T--) run_case();
	return 0;
}
int N;
int A[14];
ll ans;
void dfs(vector<vector<int>> B, int id) {
	if(id == N) {
		ll sum = 0;
		assert(B.size() == N / 2);
		for(int i = 0; i < B.size(); i++) {
			assert(B[i].size() == 2);
			sum ^= B[i][0] + B[i][1];
		}
		ans = max(ans, sum);
		return;
	}
	for(int i = 0; i < B.size(); i++) {
		if(B[i].size() == 1) {
			B[i].push_back(A[id]);
			dfs(B, id + 1);
			B[i].pop_back();
		}
	}
	if(B.size() < N / 2) {
		B.push_back({A[id]});
		dfs(B, id + 1);
		B.pop_back();
	}
}
void run_case() {
	cin >> N;
	for(int i = 0; i < N; i++) cin >> A[i];
	dfs({}, 0);
	cout << ans << endl;
}