#include<bits/stdc++.h>

#define INF 1e9
#define llINF 1e18
#define MOD 1e9+7
#define pb push_back
#define mp make_pair 
#define F first
#define S second
#define ll long long
using namespace std;

void bits (int a,int fix){
  string s="";
  while(a>0){
    char c='0'+a%2;
    a/=2;
    s+=c;
  }
  for(int i=s.size();i<fix;i++)
    s+='0';
  reverse(s.begin(),s.end());
  cout<<s<<endl;
}


int main(){
  int n;cin>>n;
  int dp[1<<15]={};
  int A[15]={};
  for(int i=0;i<n;i++)cin>>A[i];
  for(int i=0;i<(1<<n);i++){
    for(int j=0;j<n;j++){
      if(!(((i)&(1<<j))==0))continue;
      for(int k=j+1;k<n;k++){
	if(!(((i)&(1<<k))==0))continue;
	dp[i+(1<<j)+(1<<k)] = max(dp[i+(1<<j)+(1<<k)],dp[i]+(A[j]^A[k]));
      }
    }
  }
  // for(int i=0;i<(1<<(n));i++){
  //   bits(i,n);
  //   cout<<dp[i]<<endl<<endl;
  // }
  cout<<dp[(1<<n)-1]<<endl;
  return 0;
}