#include <fstream>

using namespace std;

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

int phi[1000000];

int suma(int n){

    int s = 1;
    for(int i = 2; i <= n; i++){
        phi[i] = i - 1;
    }
    for(int i = 2; i <= n; i++){
        s += 2*phi[i];
        for(int j = 2*i; j <= n; j += i){
            phi[j] -= phi[i];
        }
    }
    return s;
}

int main(){

    int n;
    fin >> n;
    fout << suma(n);
}