#include <iostream>
#include <fstream>

using namespace std;

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

    int n;
    fin >> n;

    int a[1000001];
    for (int i = 2; i <= n; i++)
        a[i] = i - 1;
    for (int i = 2; i <= n; i++)
        for (int j = i * 2; j <= n; j += i)
            a[j] -= a[i];

    long long s = 1;
    for (int i = 2; i <= n; i++)
        s += a[i] * 2;

    fout << s << endl;
}