#include <fstream>

using namespace std;

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

long long n,k,v[1000010];

int calcul (long long n)
{
     for (int i = 1; i <= n; i++)
        v[i] = i;

    for (int i = 2; i <= n; i++)
        if (v[i] == i)
            for (int j = i; j <= n; j += i)
            {
                v[j] /= i;
                v[j] *= (i-1);
            }
    for(int i = 2; i <= n; i++)
        k += v[i];
     return 2*k+1;
}

int main()
{

    f >> n;
   g << calcul (n);
}