#include<fstream.h>
#define dim 100000
unsigned long (*v)=new unsigned long[dim];
ifstream f("oo.in");
ofstream g("oo.out");
int main()
{unsigned long n,i,sum,maxim,j,k;
 f>>n;
 f>>v[1];
 for(i=2;i<=n;i++)
  {f>>v[i];v[i-1]+=v[i];}
 v[n]+=v[1]-v[2];
 unsigned long nn=n-2;
 k=1;maxim=v[k];
 for(i=4;i<=nn;i++)
  {v[i]+=maxim;
   k++;
   if(v[k]>maxim) maxim=v[k];
  }
 if((v[2]>v[1])||(v[3]>v[1]))
  {for(i=nn;i<=n;i++)
    {maxim=0;
     for(j=(i-3);j>=2;j--) if(maxim<v[j]) maxim=v[j];
     v[i]+=maxim;
    }
  }
 for(i=1;i<=n;i++) if(v[i]>maxim) maxim=v[i];
 f.close();
 g<<maxim<<'\n';
 g.close();
 return 0;
}