#include <fstream>

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

int main()
{
    int n,x,z,a[10000],b,c;
    f>>n;
    x=1;
    for(int i=1;i<=n;i++){
        a[i]=x;
        x++;
    }
    z=0;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            b=a[i];
            c=a[j];
            while(b!=c){
                if(b>c) b=b-c;
                else c=c-b;
            }
            if(b==1){
                g<<a[i]<<" "<<a[j]<<endl;
                z++;
            }
        }
    }
    g<<z;
    f.close();g.close();
}