N = int(input())
prime = [2,3] +[1] * 98;
length = 2;
prod = 1;
for i in range(100):
	prod *= prime[i]
	if prod > N:
		print(i)
		exit(0)
	if length == i+1:
		for j in range(prime[i]+2,N):
			is_prime = 1
			for i in range(length):
				if j % prime[i] == 0:
					is_prime = 0
					break
			if is_prime == 1:
				prime[length] = j
				length += 1
				break