#include<fstream>
using namespace std;
ifstream f("oo.in");
ofstream g("oo.out");
int a[100001],b[100001];
int max(int a, int b)
{
	if (a>b) return a;
	return b;
}
void rez(int c, int n,int &s)
{
	int i;
	b[c-2]=0;
	b[c-1]=a[c-1]+a[c-2];
	for (i=c;i<=n;i++){
		b[i]=max(b[i-1],b[i-3]+a[i-1]+a[i]);
		s=max(b[i],s);
	}
}
int main()
{
	int n,i;
	f>>n;
	for (i=1;i<=n;i++)
		f>>a[i];
	if (n==2)
	{
		g<<a[1]+a[2];return 0;}
	a[n+1]=a[1];
	int s=0;
	rez(3,n-1,s);
	rez(4,n,s);
	rez(5,n,s);
	g<<s;
}