#include <fstream>
using namespace std;

#define NMAX 1000005

int e[NMAX];

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

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

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

    long long rez = 0;
    for (int i = 2; i <= n; ++i) {
        rez += e[i];
    }

    rez *= 2;
    rez++;

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