#include<stdio.h>
#include<algorithm>
using namespace std;
int N,a[100010],s[100000];
int dinam(int x)
{
    for(int i=0;i<=N;++i)
        s[i]=0;
    s[x]=a[x-1]+a[x];
    int ma=s[x];
    for(int i=x+3;i<=N+x-3;++i)
    {
        if(i>=5)
        {
            s[i]=a[i-1]+a[i]+max(max(s[i-3],s[i-4]),s[i-5]);
            if(s[i]>ma)
                ma=s[i];
        }
        else
        {
            s[i]=a[i-1]+a[i]+max(s[i-3],s[i-4]);
            if(s[i]>ma)
                ma=s[i];
        }
    }

    return ma;
}
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[0]=a[N];
    if(N<=5)
    {
        int m=0;
        for(int i=1;i<=N;++i)
            if(a[i-1]+a[i]>m)
                m=a[i-1]+a[i];
        printf("%d",m);
        return 0;
    }
    printf("%d",max(max(dinam(1),dinam(2)),dinam(3)));
    return 0;
}