#include <fstream>
#include <iostream>

using namespace std;

int main() {

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

    int n;
    in >> n;

    int* v = new int[1000001];
    for (int i = 1; i <= n; i++) v[i] = i - 1;

    long long t = 1;
    for (int i = 2; i <= n; i++) {
        for (int j = 2 * i; j <= n; j += i)
            v[j] -= v[i];
        t += 2 * v[i];
    }

    delete [] v;
    cout << t;
    out << t;

    return 0;
}