N = int(input())

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

now = 1
for i in range(len(prime)):
    if now * prime[i] > N:
        print(i)
        exit()
    now *= prime[i]