def Eratosthenes(N):
  is_prime = [1 for i in range(N+1)]
  is_prime[0] = is_prime[1] = 0
  P = []
  for p in range(2,N+1):
    if is_prime[p] == 0:
      continue
    P.append(p)
    for d in range(2,N//p+1):
      q = p*d
      is_prime[q] = 0
  return P

P = Eratosthenes(200000)

N = int(input())
ans = 0
for p in P:
  if p == 2:
    ans = 1
    g = 2
    continue
  if g * p <= N:
    ans += 1
    g * p
  else:
    break
print(ans)