// Fractii.cpp : Defines the entry point for the console application.
//

//#include "stdafx.h"
#include <fstream>
#include <vector>
#include <algorithm>
#include <iostream>

using std::ifstream;
int N;

inline void readData() {
	ifstream f{ "fractii.in" };
	f >> N;
}

using std::vector;
using std::for_each;

long long getNumberOfFrac() {

	vector <int> primeWith( N + 1 );

	for_each(primeWith.begin() + 1, primeWith.end(), [](int &value) {
		static int  i = -1;
		value = ++i;
	});

	long long result = 0;

	for (int i = 2; i <= N; ++i) {
		for (int j = 2 * i; j <= N; j += i)primeWith[j] -= primeWith[i];
		result += primeWith[i] * 2;
	}
	
	return 1 + result;
}

using std::ofstream;


int main(){

	readData();

	ofstream g{ "fractii.out" };

	g << getNumberOfFrac();
	
    return 0;
}