#include<cstdio>
#include<queue>
#include<utility>
#include<cstring>
#include<stack>
#include<algorithm>
#include<cmath>
#include<iostream>
#include<map>
#include<set>
#include<vector>
#define REP(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
int N,m=-1;
vector<int> sets(0);
bool bo[16384];
void solve(int code,int mochi,int d){
  int back=code;
  if(code == 0){
    m = max(m,mochi);
    return;
  }
  else{
    for(int i=d;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);
            solve(code,mochi^(sets[i]+sets[j]),1);
            code = code ^ (1 << j);
        }
      }
    }
    if(d == 0)
      return;
    code = back;
    }
  }
}

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