#include <cstdio>
using namespace std;
int n,i,j,k,oo[10000];
long long a[10000],rez;
long mx(long long a, long long b){return a>b ? a : b;}
int main()
{
    freopen("oo.in","r",stdin);
    freopen("oo.out","w",stdout);
    scanf("%d",&n);
    for(i=0;i<n;i++)
        scanf("%d",&oo[i]);
    if(n==2)rez==oo[1]+oo[0];
    else
    {
        for(k=0;k<2;k=(k+1)%n)
        {
            a[k]=0;
            a[(k+1)%n]=0;
            a[(k+2)%n]=oo[(k+1)%n]+oo[(k+2)%n];
            for(i=(k+3)%n;i!=k;i=(i+1)%n)
                a[i]=mx(a[(i-1+n)%n],a[(i-3+n)%n]+oo[(i-1+n)%n]+oo[i]);
            rez=mx(rez, a[(k-1+n)%n]);
        }
    }
    printf("%lld\n",rez);
    return 0;
}