#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

const long long MAX = 5100000;
const long long INF = 1LL << 60;
const long long mod = 1000000007LL;
//const long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;

vector<vector<ll>> dp;
ll N;
vector<ll> a;

ll dfs(ll S, ll pre) {
	if (pre != -1 && dp[S][pre] != -1) {
		return dp[S][pre];
	}
	if (S == (1LL << N) - 1) return 0;
	ll res = 0;
	ll cnt = 0;
	for (ll i = 0; i < N; i++) {
		if ((S >> i) & 1) cnt++;
	}

	for (ll i = 0; i < N; i++) {
		if (!((S >> i) & 1)) {
			if (cnt & 1) {
				chmax(res, dfs((S + (1LL << i)), i) + (a[i] ^ a[pre]));
			}

			else chmax(res, dfs((S + (1LL << i)), i));
		}
	}

	if (pre == -1) return res;
	else return dp[S][pre] = res;

}
int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/
	scanf("%lld", &N);
	a.resize(N); for (ll i = 0; i < N; i++) scanf("%lld", &a[i]);
	dp = vector<vector<ll>>(1 << N, vector<ll>(N, -1));
	
	cout << dfs(0, -1) << endl;
	return 0;
}