#include <fstream>

using namespace std;

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

int phi[1000005];

void ciurulet () {
    for (int i = 1; i <= 1000005; ++i) {
        phi[i] = i - 1;
    }
    for (int i = 2; i <= 1000005; ++i) {
        for (int j = 2 * i; j <= 500000; j += i)
            phi[j] -= phi[i];
    }
}
int main()
{
    int i, n;
    f >> n;
    ciurulet();
    int sum = 0;
    for (i = 2; i <= n; ++i) {
        sum += phi[i];
    }
    g << 2 * sum + 1 << "\n";
    return 0;
}