#include <iostream>
#include <string>
#include <utility>
#include <algorithm>
#include <map>
#include <set>
#include <vector>
#include <cmath>
#include <cstdlib>
#include <queue>
#include <stack>
#include <iomanip>


using namespace std;

#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(ll i = m;i < n;i++)
#define FORR(i, m, n) for(ll i = m;i >= n;i--)
#define REPO(i, n) for(int i = 1;i <= n;i++)
#define ll long long
#define INF 1999999999
#define MINF -1999999999
#define INF64 1999999999999999999
#define ALL(n) n.begin(),n.end()
#define MOD 1000000007


ll n, s[20], dp[100000];
int main() {
	cin >> n;
	REP(i, n) cin >> s[i];
	REP(i, 1 << n) {
		REP(j, n) {
			if (!(i & 1 << j)) {
				REP(k, n) {
					if (j != k and !(i & 1 << k)) {
						dp[i + (1 << j) + (1 << k)] = max(dp[i + (1 << j) + (1 << k)], dp[i] + (s[j] xor s[k]));
					}
				}
			}
		}
	}
	cout << dp[(1 << n) - 1] << endl;
}