def sieve_of_eratosthenes(n):
    candidate = list(range(2, n+1))
    prime = []
    limit = n**0.5 + 1
    while True:
        p = candidate[0] 
        if limit <= p:
            prime.extend(candidate)
            break
        prime.append(p)
        candidate = [i for i in candidate if i % p != 0]
    return prime
N=int(input())
prime = sieve_of_eratosthenes(N)
s=0
prime2=[i for i in prime if i<=800]
for i in range(len(prime2)):
  if (prime2[i]**2)-2 in prime:
    s+=1
print(s*2-1)