#include<fstream.h>
main()
{int k,n;
 ifstream g("lacate.in");
 ofstream h("lacate.out");
 g>>n;
 h<<n<<" 2"<<'\n';
 for(k=1;k<n;k++)
  h<<k<<" "<<k+1<<'\n';
 h<<n<<" 1"<<'\n';
 g.close();
 h.close();
 return 0;
}