#include "bits/stdc++.h"

using namespace std;

using ll = long long;
using ld = long double;

const int INF = (1 << 30) - 1;
const ll INF64 = ((ll)1 << 62) - 1;
const double PI = 3.1415926535897932384626433832795;

const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { -1, 0, 1, 0 };

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	int n;
	cin >> n;

	vector<int> a(n);
	for (auto& v : a) {
		cin >> v;
	}

	vector<int> dp(1 << 14);
	for (int k = 0; k < (1 << n); k++) {
		for (int i = 0; i < n; i++) {
			for (int j = i + 1; j < n; j++) {
				if (k & (1 << i) || k & (1 << j)) {
					continue;
				}

				dp[k + (1 << i) + (1 << j)] = max(dp[k + (1 << i) + (1 << j)], dp[k] +(a[i] ^ a[j]));
			}
		}
	}

	cout << dp[(1 << n) - 1] << endl;
	return 0;
}