#include <fstream>
#include <vector>

using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");

int main() {
    int N;
    fin >> N;

    vector<int> phi(N + 1);

    for (int i = 1; i <= N; i++) {
        phi[i] = i;
    }

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

    long long result = 0;
    for (int i = 1; i <= N; i++) {
        result += phi[i];
    }

    fout << result;

    return 0;
}