N = int(input())

primes = []
mu = bytearray([3]) * (N + 1)
mu[1] = 2

for i in range(2, N + 1):
	if mu[i] == 3:
		primes.append(i)
		mu[i] = 0
	for p in primes:
		idx = i * p
		if idx > N:
			break
		if i % p == 0:
			mu[idx] = 1
			break
		mu[idx] = 2 - mu[i]

print(sum(mu) - 3 - N)