#include <fstream>
using namespace std;
ifstream in("oo.in");
ofstream out("oo.out");
int n,a[100001],s;
int oo(int s,int f)
{ int d[100001]={0};
  d[s]=0;
  d[s+1]=a[s]+a[s+1];
  d[s+2]=d[s+1];
  d[s+3]=d[s+1];
  for(int i=s+4;i<=f;i++)
    d[i]=max(d[i-3]+a[i]+a[i-1],d[i-1]);
  return d[f];
}
int main()
{ in>>n;
  for(int i=1;i<=n;i++)
    in>>a[i];
  a[0]=a[n];
  s=max(s,oo(0,n-2));
  s=max(s,oo(1,n-1));
  s=max(s,oo(2,n));
  out<<s<<'\n';
  in.close();
  out.close();
  return 0;
}