#include<bits/stdc++.h>

using namespace std;

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

const int DIM = 1e6;
int phi[DIM + 5];

inline void prelucru(){
    for(int i = 1 ; i <= DIM ; i++) phi[i] = i;
    for(int i = 2 ; i <= DIM ; i++){
        if(phi[i] == i){
            for(int j = i ; j <= DIM ; j += i) phi[j] = phi[j] / i * (i - 1);
        }
    }
}

int main(){
    int n; fin >> n;
    prelucru();
    long long rez=  1;
    for(int i = 2 ; i <= n ; i++) rez += 2 * phi[i];
    fout << rez;
}