#include <fstream>

using namespace std;
ifstream in ("oo.in");
ofstream out ("oo.out");

int s[100000];

int main()
{
    int c,i,a,b,smax=0,scrt=0,n;
    in>>n>>a;
    c=a;
    for(i=1;i<n;i++)
    {
        in>>b;
        s[i]=a+b;
        a=b;
    }

    s[n]=a+c;

    for(i=1;i<=3;i++)
    {
        scrt=s[i];
        for(int j=i+3;j<=n;j+=3)
        {
            if(j==n)
            {
                if(i!=1)
                    scrt+=s[j];
            }
            else
                scrt+=s[j];
        }
        if(scrt>smax)
            smax=scrt;
    }
    out<<smax;

    return 0;
}