#include<stdio.h>
#include<algorithm>
using namespace std;
int max2,n,a[100007],d[100007];
int main()
{
	freopen("oo.in","r",stdin);
	freopen("oo.out","w",stdout);
	scanf("%d",&n);
	for(int i=1;i<=n;++i)
		scanf("%d",&a[i]);
	a[n+1]=a[1];
	
	//caz 1
	d[1]=0;
	d[2]+=a[1]+a[2];
	for(int i=3;i<=n-1;++i)
	{
		d[i]=max(d[i-1],d[i-3]+a[i-1]+a[i]);
		max2=max(d[i],max2);
	}
	
	//caz 2
	d[2]=0;
	d[3]=a[2]+a[3];
	for(int i=4;i<=n;++i)
	{
		d[i]=max(d[i-1],d[i-3]+a[i-1]+a[i]);
		max2=max(d[i],max2);
	}
	
	//caz 3 
	d[3]=0;
	d[4]=a[3]+a[4];
	for(int i=5;i<=n+1;++i)
	{
		d[i]=max(d[i-1],d[i-3]+a[i-1]+a[i]);
		max2=max(d[i],max2);
	}
	printf("%d\n",max2);
	return 0;
}