N = int(input())

def eratosthenes(n):
    sieve = [True] * (n + 1)
    for i in range(int(n**0.5) + 1):
        if i < 2:
            sieve[i] = False
        elif sieve[i]:
            for j in range(2, n//i + 1):
                sieve[i * j] = False
    ans = []
    for i in range(n+1):
        if sieve[i]:
            ans.append(i)
    return ans

prime = eratosthenes(10000)
SUM = 1
for i in range(len(prime)):
    SUM *= prime[i]
    if SUM > N:
        print(i)
        break