#include <stdio.h>
int i,j,k,n;
int main()
{
 FILE*g=fopen("tije.out","w");
 FILE*f=fopen("tije.in","r");
 fscanf(f,"%d",&n);
 for (i=n-1; i>=1; i--)
   {
    for (k=n+1; k>=2; k--)
      for (j=1; j<=i; j++)
        fprintf(g,"%d %d\n",k-1,k);
    for (j=1; j<=i; j++)
      fprintf(g,"%d %d\n",n+1,1); 
   }
 return 0;
}