#include <iostream>
#include <fstream>
#include <math.h>
#include <vector>
using namespace std;

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

int n;
long long m = 1;
int *phi;

void citire(){
    in >> n;
    phi = new int[n + 1];
}

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

void scriere(){
    out << m;
}

int main(){
    citire();
    rezolvare();
    scriere();
    return 0;
}