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

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

const int MAX_N = 1000005;

int n;
int eulerIndicator[MAX_N];
long long answer;

void HandleInput() {
    fin >> n;
}

void GenerateEulerIndicator() {
    for (int i = 1; i <= n; i++) {
        eulerIndicator[i] = i;
    }

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

void ComputeAnswer() {
    for (int i = 1; i <= n; i++) {
        answer += eulerIndicator[i];
    }
    answer = answer * 2 - 1;
}

void HandleOutput() {
    fout << answer << '\n';
}

int main() {
    HandleInput();
    GenerateEulerIndicator();
    ComputeAnswer();
    HandleOutput();

    return 0;
}