N = int(input())

primes = [0] * 665000
prime_num = 0
is_prime = bytearray([1]) * (N + 1)
mu = bytearray([0]) * (N + 1)
mu[1] = 2

for i in range(2, N + 1):
	if is_prime[i]:
		primes[prime_num] = i
		prime_num += 1
		mu[i] = 0
	for j in range(prime_num):
		p = primes[j]
		idx = i * p
		if idx > N:
			break
		is_prime[idx] = 0
		if i % p == 0:
			mu[idx] = 1
			break
		mu[idx] = 2 - mu[i]

print(sum(mu) - N)