#include <iostream>

#include <fstream>

#include <bitset>



using namespace std;



long long fractii[1000001];

int n;



int phi[1000001 + 1], prime[1000001/10], sz;

bitset <1000001 + 1> mark;



int main(){

    ifstream f("fractii.in");

    ofstream g("fractii.out");



    for (int i = 2; i <= 1000001; i++ ){

        if(!mark[i]){

            phi[i] = i-1;

            prime[sz++]= i;

        }

        for (int j=0; j<sz && prime[j]*i <= 1000001; j++ ){

            mark[prime[j]*i]=1;

            if(i%prime[j]==0){

                  phi[i*prime[j]] = phi[i]*prime[j];

                  break;

            }

            else phi[i*prime[j]] = phi[i]*(prime[j]-1 );

        }

    }

    f >> n;

    fractii[0] = 1;

    fractii[1] = 2;

    for(int i = 2; i <= n; i++){

        fractii[i] = fractii[i-1] + phi[i];

    }

    g << 2*fractii[n] - 3;

}