n = int(input())
p = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47]
a = 1
ans = 0
for i in range(len(p)):
	a *= p[i]
	if a <= n:
		ans = i + 1
print(ans)