#include <fstream>
using namespace std;

const int MAX_N = 1000002;

int N;
int phi[MAX_N];
long long int ans;

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

    f >> N;

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

    g << ans << "\n";

    f.close();
    g.close();

    return 0;
}