#include <fstream>

using namespace std;

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

int a[1000100], n;

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

void solve()
{
    long long rez = 1;
    for(int i = 2; i<=n; i++)
    {
        rez+=2*a[i];
    }
    g<<rez;
}

int main() {
    f>>n;
    sir();
    solve();
    return 0;
}