#include <fstream>

using namespace std;

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

int phi[1000100], n, S=1;

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

int main()
{
    f >> n;
    calculeazaPhi();
    for(int i=1; i<=n; i++) S+=2*phi[i];
    g << S << '\n';
    return 0;
}