#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int i,j,nr,N,n,p;
int dip (int a,int b)
{ p=2;
	while (p!=0&&p!=1)
{if(a>=b){a=a-b;p=a;}
   else{b=b-a;p=b;}}
if(p==0)return 1;
  
return 0;
}

int main()
{nr=0;f>>N;
	for(i=2;i<=N;i++)
	for(j=2;j<=N;j++)
		{   if(i!=j+1&&i+1!=j)if(i!=j&&dip(i,j)==0){nr=nr+1;cout<<i<<'/'<<j<<' ';}}
g<<nr+N*2-1+(N-2)*2;
f.close();
g.close();
return 0;}