#include<iostream>
#include<fstream>
using namespace std;

ifstream f("oo.in");
ofstream g("oo.out");

int n,a[100000],v[100000],s;

int max(int c, int d)
{
	if(c>d) return c;
	else
		return d;
}

void rez(int x, int y)
{
	v[x-2]=0;
	v[x-1]=a[x-1]+a[x-2];
	for(int i=x;i<=y;i++)
	{
		v[i]=max(v[i-1], v[i-3]+a[i]+a[i-1]);
		s=max(s,v[i]);
	}
}
	
int main()
{
	int i;
	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<<s;
}