#include<fstream>
#include<cstring>
using namespace std;
ifstream cin("oo.in");
ofstream cout("oo.out");
#define NMAX 100010
int n,i,a[NMAX],b[NMAX],r1=0,r2=0,r3=0;
int main()
{
    cin>>n;
    for (i=1;i<n;i++)
    {
        cin>>a[i];
        if (i==1) b[i]=a[i];
          else if (i<=3) b[i]=max(a[i-1]+a[i],b[i-1]);
            else b[i]=max(b[i-3]+a[i-1]+a[i],b[i-1]);
        r1=max(r1,b[i]);
    }
    cin>>a[n];
    memset(b,0,sizeof b);
    a[1]+=a[n];
    for (i=1;i<n-1;i++)
    {
        if (i==1) b[i]=a[i];
          else if (i<=3) b[i]=max(a[i-1]+a[i],b[i-1]);
            else b[i]=max(b[i-3]+a[i]+a[i-1],b[i-1]);
        r2=max(r2,b[i]);
    }
    memset(b,0,sizeof b);
    for (i=2;i<=n;i++)
    {
        cin>>a[i];
        if (i==2) b[i]=a[i];
          else if (i<=4) b[i]=max(a[i-1]+a[i],b[i-1]);
            else b[i]=max(b[i-3]+a[i-1]+a[i],b[i-1]);
        r3=max(r3,b[i]);
    }
   // cout<<r1<<" "<<r2<<" "<<r3<<"\n";
    cout<<max(r3,max(r1,r2));
    return 0;
}