/******************************************************************************
Online C++ Compiler.
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*******************************************************************************/
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long int ll;
int main(){
int n; cin>>n;
ll sum=0;
vector<int>v(n);
for (int i=0; i<n; i++){
cin>>v[i];
sum+=v[i];
}sort(v.begin(), v.end());
for (int i=n-3; i>=0; i-=3) sum-=v[i];
cout<<sum<<endl;
return 0;
}
