#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int dumb(int n) {
	ll sol = 0;
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= n; j++) {
			if (__gcd(i, j) == 1) {
				sol++;
			}
		}
	}
	return sol;
}

int smart(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 ("flip.in", "r", stdin);
	freopen ("flip.out", "w", stdout);
#endif

	if (0) {
		for (int i = 1; i <= 100; i++) {
			assert(smart(i) == dumb(i));
		}
	}

	int n;
	while (cin >> n) {
		cout << smart(n) << "\n";
	}
	
	return 0;
}