#include<bits/stdc++.h>
using namespace std;
ifstream fin("oo.in");
ofstream fout("oo.out");

int n;
int s1,s2;

int main()
{
    int x,k=1,k2=1;
    fin>>n;
    for(int i=1;i<=n;i++)
    {
        fin>>x;
        if(k%3!=0)
            s1=s1+x;
        if(k%4!=0 && k!=1)
            s2=s2+x;
        k++;
    }
    if(s2>s1)
        fout<<s2;
    else
        fout<<s1;
    return 0;
}