#include<iostream>
#include<climits>
#include<set>
#include<map>
#include<vector>
#include<string>
#include<algorithm>
#include<math.h>
#include<queue>
#include<deque>
#include<stack>
#include<assert.h>
#include<numeric>
#include<bitset>

#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()

typedef long long ll;
using namespace std;
const int inf = INT_MAX / 2;
const ll infl = 1LL << 62;
const double PI = 2 * acos(0.0);
template<class T>bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; }
ll gcd(ll a, ll b) { return a ? gcd(b % a, a) : b; }

int n;
int A[20];
int dp[20000];
int rec(int S) {
	if (S == 0) return 0;

	int& ret = dp[S];

	if (ret != 0) return ret;


	for (int i = 0; i < n; i++) for (int j = i + 1; j < n; j++) {
		if ((S & 1 << i) && (S & 1 << j)) {
			int score = A[i] ^ A[j];
			int pair = (1 << i) + (1 << j);
			chmax(ret, rec(S ^ pair) + score);
		}
	}

	return ret;
}
int main() {
	cin >> n;
	for (int i = 0; i < n; i++) cin >> A[i];

	cout << rec((1 << n) - 1) << endl;
}