#include <fstream>
using namespace std;

const int VMAX = 1e6;
int e[VMAX + 1];

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

    int n;
    in >> n;

    for (int i = 1; i <= n; i++) e[i] = i;
    for (int i = 2; i <= n; i++) {
        if (e[i] == i) { // e[i] nu a fost modf deci i prim
            for (int m = i; m <= n; m += i) {
                e[m] = e[m] / i * (i - 1);
            }
        }
    }
    long long s = 0;
    for (int i = 2; i <= n; i++) {
        s += 2 * e[i];
    }
    s++;
    out << s << "\n";

    in.close(); out.close();
    return 0;
}