#include<cstdio>
#include<queue>
#include<utility>
#include<cstring>
#include<stack>
#include<algorithm>
#include<cmath>
#include<iostream>
#include<map>
#include<set>
#include<vector>
#define MAX_N 100001
#define INF_INT 2147483647
#define INF_LL 9223372036854775807
#define REP(i,n) for(int i=0;i<(int)(n);i++)
void init(int n);
int find(int n);
void unite(int x,int y);
bool same(int x, int y);
int dx[4] = {1,0,0,-1};
int dy[4] = {0,1,-1,0};
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
bool cmp_P(const P &a,const P &b){
  return a.second < b.second;
}
int N,m=-1;
vector<int> sets(0);
vector<int> est(14);
int solve(int code,int mochi){
  int back=code;
  if(code == 0){
    int tmp =0;
    REP(i,N/2){
      tmp = tmp^est[i];
    }
    m = max(m,tmp);
    return 0;
  }
  else{
    for(int i=0;i<N;i++){
      if((code >> i)&1){
        code = code ^ (1 << i);
        for(int j=i+1;j<N;j++){
          if((code >> j) & 1){
            code = code ^ (1 << j);
            est[mochi] = sets[i]+sets[j];
            solve(code,mochi-1);
            code = code ^ (1 << j);
        }
      }
    }
    code = back;
    }
  }
  return m;
}

int main()
{
  int A;
  cin >> N;
  REP(i,N){
    cin >> A;
    sets.push_back(A);
  }
  sort(sets.begin(),sets.end());
  
  solve((1 << N)-1,N/2-1);
  cout << m << endl;
  return 0;
}