N = int(input())

C = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53]

a = 1
ans = 0
i = 0
while a * C[i] < N:
	a *= C[i]
	ans += 1
	i += 1
print(ans)