#include <iostream>
#include <fstream>
#define ull unsigned long long
using namespace std;
ifstream f ("fractii.in");
ofstream g ("fractii.out");
ull n,i,nr;
ull phi (ull x)
{
    ull i,sol=x;
    for (i=2;i*i<=x;i++)
    {
        if (x%i==0)
        {
            while (x%i==0) x/=i;
            sol=(sol/i)*(i-1);
        }
    }
    if (x>1) sol=sol/x*(x-1);
    return sol;
}
int main()
{
    f>>n;
    nr=1;
    for (i=2;i<=n;i++)
    {
        nr=nr+2*phi(i);
    }
    g<<nr;
    return 0;
}