#include <cstdio>
#include <fstream>
#include<algorithm>
#include<vector>
using namespace std;

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

int N;
int v[1000010];


int main() {

	long long r = 0;
	in >> N;

	for (int i = 2;i <= N;++i)
		v[i] = i - 1;

	for (int i = 2;i <= N;++i)
	{

		r += 2 * v[i];
		for (int j = i + i;j <= N;j += i)
		{
			v[j] -= v[i];
		}

	}
	out << r+1;

	return 0;
}