#include<fstream>
#include<iostream>
using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

int cmmdc(unsigned long a,unsigned long b)
{
	while(a!=b)
		if(a>b)
			a=a-b;
		else
			b=b-a;
	return a;
}
int main()
{
	unsigned long n,i,j,nr=0;
	f>>n;
	for(i=2;i<=n;i++)
		for(j=2;j<=n;j++)
			if(j!=i&&!(i%j==0||j%i==0))
				if(cmmdc(i,j)==1)
				{nr++;cout<<i<<" "<<j<<endl;}					
	nr+=n+n-1;
	cout<<nr;
	return 0;
}