#include <cstdio>

using namespace std;
int i,n,oo[100002],a[100002],mx,j;
int main()
{
    freopen("oo.in","r",stdin);
    freopen("oo.out","w",stdout);
    scanf("%d",&n);
    for (i=1;i<=n;i++) scanf("%d",&a[i]);
    a[n+1]=a[1];
    for (i=1;i<=3;i++)
    {
    	for (j=1;j<=n;j++) oo[i+1]=a[i]+a[i+1];
    	for (j=i+2;j<=n-2+i;j++) {
            oo[j]=oo[j-1];
            if (oo[j-3]+a[j-1]+a[j]>oo[j])
                oo[j]=oo[j-3]+a[j-1]+a[j];
        }
        if (oo[n-2+i]>mx) mx=oo[n-2+i];
    }
    printf("%d ",mx);
    return 0;
}