#include <fstream>
using namespace std;

#define NMAX 1000005

int cnt[NMAX];

int main() {
    int n;
    ifstream("fractii.in") >> n;

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

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

    ofstream("fractii.out") << rez;
    return 0;
}