#include <fstream>
#include <vector>
using namespace std;

ifstream is("fractii.in");
ofstream os("fractii.out");

long long Phi[1000001];
long long N;

void Sieve();

int main()
{
    is >> N;
    Sieve();
    long long S(0);
    for ( int i = 2; i <= N; ++i )
    {
        S += Phi[i];
    }
    os << S*2+1;

    is.close();
    os.close();
}

void Sieve()
{
    for ( int i = 1; i <= N; ++i )
        Phi[i] = i-1;
    for (int i = 2; i <= N; ++i)
        for (int j = 2*i; j <= N; j += i)
            Phi[j] -= Phi[i];
}