N = int(input())

primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97]
x = 1
for i, p in enumerate(primes):
    x *= p
    if x > N:
        break
print(i)