#include <bits/stdc++.h>
#define DIM 1000002

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

int N;
int F[DIM],S;

int main(){

    fin >> N;

    for(int i=2;i<=N;i++)
        F[i]=i;
    for(int i=2;i<=N;i++)
        if(F[i]==i){
            for(int j=i;j<=N;j+=i)
                F[j] = F[j]/i*(i-1);
        }

    for(int i=2;i<=N;i++)
        S += F[i];

    fout << 2 * S + 1;



}