#include <bits/stdc++.h>
#define ll long long

using namespace std;

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

int n;
ll ans, cnt[1000100], phi[1000100];

int main() {
	in >> n;
	for (int i = 1; i <= n; i++)
		phi[i] = i;
	for (int i = 2; i <= n; i++) {	
		if (cnt[i])
			continue;
		phi[i]--;
		cnt[i]++;
		for (int j = i + i; j <= n; j += i) {
			phi[j] -= j / i;
			cnt[j]++;
		}
	}
	for (int i = 1; i <= n; i++)
		ans += phi[i] + cnt[i] - 1;
	ans++;
	out << 2LL * ans - 1LL;
	return 0;
}