#include <iostream>
#include <fstream>

using namespace std;

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

int f[1000001];

int main() {
    int n;
    if (!(in >> n)) return 0;

    for (int i = 1; i <= n; i++) {
        f[i] = i;
    }

    for (int i = 2; i <= n; i++) {
        if (f[i] == i) {
            for (int j = i; j <= n; j += i) {
                f[j] = f[j] / i * (i - 1);
            }
        }
    }

    long long suma = 0;
    for (int i = 1; i <= n; i++) {
        suma += f[i];
    }

    out << 2 * suma - 1 << endl;

    return 0;
}