#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define revrep(i,a,b) for(int i=a;i>b;i--)
#define int long long

const int inf = 100100100100000;
const int mod = 1000000007;
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};

int input(){int tmp;cin >> tmp;return tmp;}
string raw_input(){string tmp;cin >> tmp;return tmp;}
string readline(){string s;getline(cin, s);return s;}
void print(int n){cout << n << endl;}
void print(vector<int> arr){cout << arr[0];rep(i,1,arr.size()) cout << " " << arr[i];cout << endl;}
void print(string s){cout << s << endl;}
void print(pair<int, int> p){cout << p.first << " " << p.second;}
void print(vector<vector<int>> arr){rep(i,0,arr.size()){print(arr[i]);}}
void print(double n){cout << n << endl;}


//main-----------------------------------------------------------------------------
int n;
int arr[14];
vector<int> bitdp(1<<14,-1);


int dfs(int s){
    if(bitdp[s] > -1) return bitdp[s];

    if(s == (1<<n)-1) return 0;

    int atk = 0;
    rep(i,0,n){
        rep(j,i+1,n){
            if( !(s & (1 << i)) && !(s & (1 << j)) ){
                atk = max(atk, ((arr[i]^arr[j]) + dfs(s + (1<<i) + (1<<j))));
            }
        }
    }

    bitdp[s] = atk;
    return atk;


}

signed main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    n = input();
    rep(i,0,n) cin >> arr[i];

    print(dfs(0));
   





}