#include <fstream.h>
int i,j,k,n;
int main()
{
 ifstream f("tije.in");
 ofstream q("tije.out");
 f >> n;
 for (i=n-1; i>=1; i--)
   {
    for (k=n+1; k>=2; k--)
      for (j=1; j<=i; j++)
        q << k-1 <<" "<<k <<"\n";
    for (j=1; j<=i; j++)
      q << n+1 << " " << "1" <<"\n"; 
   }
 return 0;
}