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

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