#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <unordered_map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
using namespace std;

long long MOD = 1000000007;

int N;
vector<long long> A;
vector<long long> X;

long long func( int a, long long s ) {

    if ( X[a] != -1 ) { return X[a]+s; }

    vector<int> B;
    for ( int i = 0; i < N; i++ ) {
        if ( ((1<<i)&a) == 0 ) { B.push_back(i); }
    }

    long long best = s;
    for ( int i = 0; i < B.size(); i++ ) {
    for ( int j = i+1; j < B.size(); j++ ) {
        best = max( best, func( a | (1<<B[i]) | (1<<B[j]), s+( A[B[i]]^A[B[j]] ) ) );
    }
    }

    X[a] = best-s;
    return best;

}

int main() {
    
    cin >> N;
    
    A.resize(N);
    X.resize(1<<N,-1);

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

    cout << func( 0,0 ) << endl;

    return 0;
}