#include "bits/stdc++.h"

using namespace std;

#define pb push_back
#define mp make_pair
constexpr int INF = 1 << 29;
constexpr int MOD = 1000000007;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;

constexpr int dx[4] = {1, 0, -1, 0};
constexpr int dy[4] = {0, 1, 0, -1};

int dfs(vector<int> &A, vector<int> &used, vector<pii> &pairs) {
	int unused = -1;
	for(int i = 0; i < used.size(); i++) {
		if (!used[i]) {
			unused = i;
		}
	}
	if (unused == -1) {
		int sum = 0;
		for(int i = 0; i < pairs.size(); i++) {
			sum += A[pairs[i].first] ^ A[pairs[i].second];
		}
		return sum;
	}
	int ret = 0;
	for(int i = 0; i < used.size(); i++) {
		if (!used[i] && unused != i) {
			used[i] = used[unused] = 1;
			pairs.push_back(mp(i, unused));
			ret = max(ret, dfs(A, used, pairs));
			pairs.pop_back();
			used[i] = used[unused] = 0;
		}
	}
	return ret;
}

int main() {
	int N;
	cin >> N;
	vector<int> A(N);
	for (int i = 0; i < N; i++) {
		cin >> A[i];
	}


	vector<int> used(N);
	vector<pii> pairs; 
	cout << dfs(A, used, pairs) << endl;

	return 0;
}