#include <iostream>
#include <fstream>

using namespace std;

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

const int NMAX = 1000000;
long long n, cnt, F[NMAX + 1];

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

int main()
{
    Phi();
    f >> n;
    for(int i = 1; i <= n; ++i)
        cnt += F[i] * 2;
    g << cnt - 1;
    f.close();
    g.close();
    return 0;
}