#include <fstream>
#define nmax 100001

using namespace std;

ifstream fin("oo.in");
ofstream fout("oo.out");

int n,v[nmax],vs[nmax],i,k,maxx,poz,s;

void citire()
{fin>>n>>v[1];
k=n;
for(i=2;i<=n;i++)
{fin>>v[i];
vs[i-1]=v[i]+v[i-1];
}
vs[n]=v[1]+v[n];

}
void maxim()
{ maxx=-1;
for(i=1;i<=n;i++)if(maxx<vs[i]){maxx=vs[i];poz=i;}

}

int main()
{citire();
while(k)
{maxim();
s+=vs[poz];
vs[poz]=vs[poz-1]=vs[poz-2]=vs[poz+1]=vs[poz+2]=-1;
k-=5;
}
fout<<s;
return 0;
}