S = input
R = range
P = print
def I(): return int(S())
def M(): return map(int, S().split())
def L(): return list(M())
def O(): return list(map(int, open(0).read().split()))
def yn(b): print("Yes" if b else "No")
biga = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
smaa = "abcdefghijklmnopqrstuvwxyz"

from sympy import nextprime

n = I()
p = 2
q = 1
c = 0
while q <= n:
	q *= p
	p = nextprime(p)
	c += 1
print(c)