#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  vector<Int> a(n);
  for(Int i=0;i<n;i++) cin>>a[i];

  Int s=1<<n;
  Int ans=0;
  for(Int b=0;b<s;b++){
    if(__builtin_popcount(b)*2!=n) continue;
    vector<Int> x,y;
    for(Int i=0;i<n;i++)
      ((b>>i)&1?x:y).emplace_back(a[i]);    
    sort(y.begin(),y.end());
    do{
      Int res=0;
      for(Int i=0;i<n/2;i++) res^=x[i]+y[i];
      chmax(ans,res);
    }while(next_permutation(y.begin(),y.end()));
  }
  
  cout<<ans<<endl;
  return 0;
}