#include <bits/stdc++.h>

#define N_MAX 1000002

using namespace std;

int n;

int phi[N_MAX];

int main()
{
	ifstream fin ("fractii.in");
	ofstream fout ("fractii.out");
	fin >> n;
	long long ans = 1;
	phi[1] = 1;
	for(int i = 2; i <= n; i++)
	{
		phi[i] += i - 1;
		ans += phi[i];
		for(int j = i + i; j <= n; j += i)
			phi[j] -= phi[i];
	}
	fout << ans * 2 - 1 << "\n";
    return 0;
}