#include <iostream>
#include <fstream>

using namespace std;

#define Nmax 1000005

int phi[Nmax];
long long sol = 0;
int N;

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

    f >> N;

    for (int i=1;i<=N;i++) phi[i]=i;

for (int i=2;i<=N;i++)
   if (phi[i]==i)
      for (int j=i;j<=N;j+=i) phi[j] /=i, phi[j] *= (i-1);

    for ( int i = 2; i <= N; ++i )
            sol += phi[i];

    g << 2*sol+1;

    return 0;
}