#include<iostream>
#include<fstream>
using namespace std;
int a[100005],v[100005],sol;
void rez(int s, int f)
{
	int i;
	v[s-2]=0;
	v[s-1]=a[s-1]+a[s-2];
	for (i=s; i<=f; i++)
	{
		v[i]=max(v[i-1], v[i-3]+a[i]+a[i-1]);
		sol=max (s, v[i]);
	}
}
int main(void)
{
	int n,i;
	fstream f,g;
	f.open("oo.in",ios::in);
	g.open("oo.out",ios::out);
	f>>n;
	for (i=1;i<=n;i++)
		f>>a[i];
	a[n+1]=a[1];
	rez(3,n-1);
	rez(4,n);
	rez(5,n+1);
	g<<sol;
	
}