import math

def makeprime(k) :
    prime = [2,3,5,7,11]

    for i in range(13, k + 1, 2) :
        if (i % 3 == 0 or i % 5 == 0 or i % 7 == 0 or i % 11 == 0) :
            continue
        limit = int(math.sqrt(i)) + 1
        isprime = False
        for x in prime :
            if (x > limit) :
                isprime = True
                break
            if (i % x == 0) :
                break
        if (isprime) :
            prime.append(i)
    
    return prime

k = int(input())
prime = makeprime(k)

i_r = 1
i_q = 3
cnt = 0

last_prime = prime[-1]
limit_r = math.sqrt(2 + k)

while (prime[i_r] <= limit_r) :
    R = prime[i_r] ** 2
    while (True) :
        Q = 2 + prime[i_q]
        if (R == Q) :
            cnt += 1
            break
        elif (Q > R or prime[i_q] == last_prime) :
            break
        i_q += 1
    i_r += 1

print(cnt * 2 + 1)