#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],r=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]);
    }
    r=b[n-1];
    cin>>a[n];
    memset(b,0,sizeof b);
    for (i=3;i<n-1;i++)
    {
        if (i==3) b[i]=a[i];
          else if (i<=5) 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]);
    }
    r=max(r,b[n-2]+a[1]+a[n]);
    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]);
    }
    r=max(r,b[n]);

    cout<<r;
    return 0;
}