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

int main()
{
    int n,i,j,k(0);
    ifstream in("fractii.in");
    ofstream out("fractii.out");
    in>>n;
    if(n==1)
    {
        out<<1;
    }
    else
    {
        k=k+n;
        for(i=2;i<=n;i++)
        {
            j=1;
            k++;
            cout<<i<< " "<<j<<endl;
            for(j=2;j<=n;j++)
            {
                if((i%j!=0)&&(j%i!=0))
                {
                    k++;
                    cout<<i<< " "<<j<<endl;
                }
            }
        }
        out<<k;
    }
    return 0;
}