#include <fstream>
#define max(a,b) (a>b)?(a):(b)
#define nr 100000
using namespace std;
ifstream f("oo.in");
ofstream g("oo.out");
int main()
{
    int i,n,j,v[nr],h[nr],s=0,max1=-1,max2=-1;
    f>>n;
    for(i=1;i<=n;i++)
    {
        f>>v[i];
    }

    v[0]=v[n];
    v[n+1]=v[1];
     max1=-1;
     h[1]=v[1]+v[2];
     h[2]=v[4]+v[5];
    for(i=3;i<=n;i++)
    {
        h[i]=max(h[i-1],(h[i-3]+v[i]+v[i+1]));
        if(h[i]>=max1)
            max1=h[i];
    }
    g<<max1<<"\n";
    return 0;
}