#include <iostream>
#include <cmath>
#include <string>
#include <algorithm>
#include <set>
#include <vector>
#include <map>
#include <list>
#include <stack>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <queue>
#define pye cout << "yes" << endl;
#define pno cout << "no" << endl;
#define pYe cout << "Yes" << endl;
#define pNo cout << "No" << endl;
#define pYE cout << "YES" << endl;
#define pNO cout << "NO" << endl;
#define prin(num) cout << num << endl;
#define max(a, b) ((a)>(b) ? (a):(b))
#define min(a, b) ((a)<(b) ? (a):(b))
#define INF 100000000000
#define MOD 1000000007LL
#define MAX_V 10005
#define MAX_E 30005
#define NIL -1
#define WHITE 0
#define BLACK 1
#define mp make_pair
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
typedef map<ll, ll> Map;

int main(void) {
    ll N, i;
    cin >> N;
    ll A[14];
    ll dp[1<<14]={0};
    ll msk;
    ll a, b;
    
    for(i=0; i<N; i++) {
        cin >> A[i];
    }
    
    for(msk=0; msk<1<<N; msk++) {
        for(a=0; a<N; a++) {
            for(b=a+1; b<N; b++) {
                if(!(msk>>a&1) && !(msk>>b&1)) {
                    dp[msk+(1<<a)+(1<<b)]=max(dp[msk+(1<<a)+(1<<b)], dp[msk]+(A[a]^A[b]));
                }
            }
        }
    }
    
    prin(dp[(1<<N)-1]);
}