#include <fstream>
using namespace std;
ofstream fout("fractii.out");
ifstream fin("fractii.in");

const int NMAX = 1000005;

int n;
long long nr[NMAX], sol = 1;

int main()
{
    fin >> n;

    for(int i=1; i<=n; i++) nr[i] = i - 1;
    for(int i=2; i<=n; i++) {
        sol += nr[i] * 2;
        for(int j=i*2; j<=n; j+=i)
            nr[j] -= nr[i];
    }

    fout << sol << '\n';
    return 0;
}