#include <iostream>

using namespace std;

int main()
{   int n,p=1,q,c=0,d,ok;
    cin>>n;
    while(p<=n){
        for(q=1;q<=n;q++){
            ok=1;
            if(q==1 && p==1){ c++; cout<<p<<' '<<q<<endl;}
            if(q!=p){




                if(q>=p){
                d=2;
                while(d<=q/2){
                    if(q%d==0 && p%d==0) ok=0;
                        d++;
                }}else{
                d=2;
                while(d<=p/2){
                    if(q%d==0 && p%d==0) ok=0;
                        d++;
                }
                }
            if(ok==1) {c++;cout<<p<<' '<<q<<endl;}
            }
        }
        p++;
        }
    cout << c << endl;
    return 0;
}