#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define fi first
#define se second
#define rep(i,s,n) for(int i = s;i<n;i++)
#define rrep(i,s,n) for(int i = (n)-1;i>=(s);i--)
#define all(v) (v).begin(),(v).end()
#define chmin(a,b) a=min((a),(b))
#define chmax(a,b) a=max((a),(b))
#define endl '\n'
#define IOS() ios_base::sync_with_stdio(0);cin.tie(0)
typedef long long ll;
typedef pair<int,int>pint;
typedef vector<int>vint;
const ll MOD=1000000007,INF=1e18;

int N;
int dp[1ll<<20];

signed main() {
    IOS();
    cin>>N;
    vint a(N);
    rep(i,0,N)cin>>a[i];
    rep(i,0,(1ll<<N)){
        rep(j,0,N){
            rep(k,0,N){
                if(j==k)continue;
                if((i&(1ll<<j))==0)continue;
                if((i&(1ll<<k))==0)continue;
                int t=i,tmp=a[j]^a[k];
                t^=1ll<<j;
                t^=1ll<<k;
                chmax(dp[i],dp[t]+tmp);
            }
        }
    }
    cout<<dp[(1ll<<N)-1]<<endl;
    
    
    
    
    
    
    
    
    
    
    
    
    
    return 0;
}