#include <cstdio>
#include <algorithm>
using namespace std;
int n,v[100005],a[100005],maxx,i;
int maxim(int por,int sf)
{
    a[por]=0;
    a[por+1]=v[por]+v[por+1];
    for(i=por+2;i<=sf;i++) a[i]=max(a[i-1],a[i-3]+v[i-1]+v[i]);
    return a[sf];
}
int main()
{
    freopen("oo.in","r",stdin);
    freopen("oo.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++) scanf("%d",&v[i]);
    v[n+1]=v[1];
    printf("%d",max(max(maxim(1,n-1),maxim(2,n)),maxim(3,n+1)));
    return 0;
}