#include<bits/stdc++.h>
using namespace std;
using ll = long long;
template<class T> using vt = vector<T>;
template<class T> using vvt = vector<vt<T>>;
template<class T> using ttt = tuple<T,T>;
using tii = tuple<int,ll>;
using vi = vector<int>;
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define pb push_back
#define mt make_tuple
#define ALL(a) (a).begin(),(a).end()
#define FST first
#define SEC second
#define DEB cerr<<"!"<<endl
#define SHOW(a,b) cerr<<(a)<<" "<<(b)<<endl
#define DIV int(1e9+7)
const int INF = (INT_MAX/2);
const ll LLINF = (LLONG_MAX/2);
const double eps = 1e-8;
//const double PI = M_PI;  
inline ll pow(ll x,ll n,ll m){ll r=1;while(n>0){if((n&1)==1)r=r*x%m;x=x*x%m;n>>=1;}return r%m;}
inline ll lcm(ll d1, ll d2){return d1 / __gcd(d1, d2) * d2;}

/*Coding Space*/
// ペアの全探索は a.begin(), a.begin() + n/2, a.end() として a[i],a[i+n/2](i = 0..n/2)
template<class T> // T は双方向イテレータ
inline constexpr bool next_patial_permitation(T first, T middle, T last){ // nP_middleを列挙
  reverse(middle, last);
  return next_permutation(first, last);
}
int main(){
  int n; cin >> n;
  vi in(n); rep(i,n) cin >> in[i];
  sort(ALL(in));
  int ans = 0;
  do{
    int tans = 0;
    rep(i,n/2)
      tans ^= in[i] + in[i + n/2];
    ans = max(ans, tans);
  }while(next_patial_permitation<vector<int>::iterator>(in.begin(), in.begin() + n/2, in.end()));
  cout << ans << endl;
}