#include <cstdio>
#include <cstring>
#include <string>
#include <iostream>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;

int d[7];
ll ans;
int n;
ll a[14];
void solve(int i){
  if(i==n/2){
    bool used[14]={};
    int x=0;
    ll ans1=0;
    for(int j=0; j<n/2; j++){
      while(used[x]) x++;
      int y=x, c=0;
      while(c<d[j]){
        y++;
        if(!used[y]){
          c++;
        }
      }
      ans1+=(a[x]^a[y]);
      used[x]=1;
      used[y]=1;
    }
    ans=max(ans, ans1);
    return;
  }
  for(int j=1; j<=n-2*i-1; j++){
    d[i]=j;
    solve(i+1);
  }
}

int main()
{
  cin>>n;
  for(int i=0; i<n; i++) cin>>a[i];
  solve(0);
  cout<<ans<<endl;
	return 0;
}