#include <iostream>
#include <fstream>
using namespace std;

long long fractii(long long n) {
    long long v[1000000];
    long long k = 0;
    for (int i = 2; i <= n; ++i) {
        v[i] = i - 1;
    }
    for (int i = 2; i <= n / 2; ++i) {
        for (int j = 2 * i; j <= n; j+=i) {
            v[j] -= v[i];
        }
    }
    for (int i = 2; i <= n; ++i) {
        k += v[i];
    }

    return k * 2 + 1;
}

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

    long long n;
    fin >> n;
    fout << fractii(n);

    fin.close();
    fout.close();
    return 0;
}