#include<iostream>
#include<fstream>
using namespace std;
unsigned cmmdc(unsigned a, unsigned b)
{unsigned r;
while(b)
	{r=a%b;
	a=b;
	b=r;
	}
return a;
}

int main()
{ifstream f("fractii.in");
ofstream g("fractii.out");
unsigned n,i,j,nr=1;
f>>n;cout<<n;
for(i=1;i<=n;i++)
	for(j=1;j<=n;j++)
		if(cmmdc(i,j)==1) {cout<<i<<" "<<j<<endl;nr++;}
g<<nr;
f.close();
g.close();
return 0;
}