p = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59]
i = 0
a = 1
n = int(input())
while a * p[i] <= n:
    a *= p[i]
    i += 1
print(i)