#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int f(int n) {
	ll sol = 0;
	vector<int> phi(n + 1);
	for (int i = 1; i <= n; i++) {
		phi[i] = i;
	}
	for (int i = 2; i <= n; i++) {
		if (phi[i] == i) {
			for (int j = i; j <= n; j += i) {
				phi[j] /= i;
				phi[j] *= (i - 1);
			}
		}
	}
	for (int i = 1; i <= n; i++) {
		sol += phi[i];
	}
	return 2 * sol - 1;
}

int main() {
#ifdef INFOARENA
	freopen ("fractii.in", "r", stdin);
	freopen ("fractii.out", "w", stdout);
#endif

	int n;
	cin >> n;
	cout << f(n) << "\n";
	
	return 0;
}