N = int(input())

ans = 1
dat = [0] * (10 ** 6)
count = 0
C = 10 ** 6
for i in range(2,N + 1):
	if dat[i] == 0:
		for j in range(i,C,i):
			dat[j] = 1
		if ans * i > N:
			print(count)
			break
		else:
			ans *= i
			count += 1