#include <fstream>
#include <iostream>
#include <cmath>
#define tip unsigned long long
#define MAX 1000001
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int main()
{
    int N, phi[MAX]; tip sol=1;
    fin>>N;
    for (int i = 1; i <= N; ++i)
        phi[i] = i-1;
    for (int i = 2; i <= N; ++i)
        for (int j = 2*i; j <= N; j += i)
            phi[j] -= phi[i];
    for(int i=1; i<=N; i++)
        sol+=2*phi[i];
    fout<<sol;
    fin.close();
    fout.close();
    return 0;
}

//folosind indicator euler