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

int numarFractiiIreductibile(int 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] *= (i - 1);
                phi[j] /= i;
            }
        }
    }
    
    int count = 0;
    for (int i = 1; i <= N; ++i) {
        count += phi[i];
    }
    
    return count;
}

int main() {
    ifstream fin("fractii.in");
    ofstream fout("fractii.out");
    int N;
    fin >> N;
    
    int rezultat = numarFractiiIreductibile(N);
    fout << rezultat ;
    
    return 0;
}