#include <bits/stdc++.h>
using namespace std;

int main()
{
	int N;
	cin >> N;
	vector<int> A(N);
	for (int i = 0; i < N; i++) {
		cin >> A[i];
	}
	int x = N / 4 * 2;
	vector<unordered_set<int>> dp(1 << N);
	dp[0].insert(0);
	for (int i = 1; i < (1 << N); i++) {
		if (__builtin_popcount(i) & 1) continue;
		if (__builtin_popcount(i) > N - x) continue;
		for (int j = 0; j < N; j++) if (i & (1 << j)) {
			for (int k = j + 1; k < N; k++) if (i & (1 << k)) {
				int t = i - (1 << j) - (1 << k);
				for (auto val : dp[t]) {
					dp[i].insert(val ^ (A[j] + A[k]));
				}
			}
		}
	}
	int res = 0;
	for (int i = 0; i < (1 << N); i++) {
		if (__builtin_popcount(i) != x) continue;
		for (auto v1 : dp[i]) {
			for (auto v2 : dp[(1 << N) - 1 - i]) {
				res = max(res, v1 ^ v2);
			}
		}
	}
	cout << res << endl;
	return 0;
}