import sys
sys.setrecursionlimit(5*10**5)
input = sys.stdin.readline
sys.set_int_max_str_digits(0)
from collections import defaultdict, deque, Counter
from heapq import heappop, heappush
from bisect import bisect_left, bisect_right
from math import gcd, lcm, factorial, perm, comb
from itertools import product, permutations, combinations
from functools import lru_cache #@lru_cache(maxsize=128)
#重複あり:list(product(list('123'),repeat = 2)),重複なし:list(permutations(list('123')))
MOD = 998244353

def get_prime(n):
    sieve = [True] * (n + 1) 
    i = 2
    while i * i <= n: 
        if sieve[i]:
            for j in range(i * i, n + 1, i):
                sieve[j] = False
        i += 1
    return [i for i in range(2, n + 1) if sieve[i]]

n = int(input())
l = get_prime(1000)
# print(l)
t=1
for i in range(20):
    t *=l[i]
    if n<t:
        print(i)
        exit()