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

le = len(primes)

for i in range(le-1):
    primes[i+1] *= primes[i]

n = int(input())

for i in range(le):
    if primes[i] < n:
        pass
    else:
        print(i)
        exit()