n=int(input())
ans=0
tmp=1
prime = [1 for i in range(10**6+1)]
p = 2
while (p * p <= n):
  if prime[p] == 1:
    tmp*=p
    if tmp<=n:
      ans+=1
    else:
      exit(print(ans))
    for i in range(p * 2, 10**6+1, p):
      prime[i] = False
  p += 1
      



print(ans)