#include<iostream.h>
#include<fstream.h>
int main ()
{
	int s=0,n,p=1,i;
fstream f;
fstream g;
f.open("fractii.in",ios::in);
g.open("fractii.out",ios::out);
	f>>n;
while(p<=n)
	{for(i=1;i<=n;i++)
		if(p%2==0 && i%2==0)
		{;}
			else
				if(p%i!=0 && i%p!=0)
		          {cout<<p<<" "<<i<<endl;
			       s++;}
p++;
cout<<endl;
	}	
	g<<s+2*n-1;
	
	
}