#include <bits/stdc++.h>
#include <stdio.h>
#include <stdlib.h>
#define MAX 1000000
using namespace std;
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");
int A[MAX+1],n;
long long int sum=0;
void ciur(){
for(int i=1;i<=MAX;i++)
    A[i]=i;
for(int i=2;i<=MAX;i++){
    if(A[i]==i){
        A[i]--;
        for(int j=2;j*i<=MAX;j++)
            A[j*i]=A[j*i]/i*(i-1);
    }
}
}
int main()
{
    ciur();
    fscanf(f,"%d",&n);
    for(int i=2;i<=n;i++){
        cout<<A[i]<<" "<<i<<'\n';
        sum+=A[i];
    }
    fprintf(g,"%lld",2*sum+1);
}