#include <iostream>
#include <fstream>
#include <vector>

using namespace std;

const int MAX_N = 1000000;

vector<int> compute_totient(int max_n) {
    vector<int> totient(max_n + 1);
    for (int i = 1; i <= max_n; ++i) {
        totient[i] = i;
    }
    for (int i = 2; i <= max_n; ++i) {
        if (totient[i] == i) { // i is a prime
            for (int j = i; j <= max_n; j += i) {
                totient[j] = totient[j] * (i - 1) / i;
            }
        }
    }
    return totient;
}

int main() {
    ifstream inFile("fractii.in");
    ofstream outFile("fractii.out");

    int N;
    inFile >> N;

    vector<int> totient = compute_totient(MAX_N);
    int count = 0;
    for (int i = 1; i <= N; ++i) {
        count += totient[i];
    }

    outFile << count << endl;

    inFile.close();
    outFile.close();

    return 0;
}