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()