from math import isqrt
N = int(input())
now = 1
ans = 0
fl = 2
while now <= N :
	ok = True
	for x in range(1, isqrt(fl) + 1) :
		ok = ok and (fl % x != 0)
	if ok :
		now *= fl
		ans += 1
	fl += 1
print(ans - 1)