import math

N = int(input())

# 0以上整数x「未満」の素数をリストに格納して返す
def primes(x):
    if x < 2: return []

    primes = [i for i in range(x)]
    primes[1] = 0 # 1は素数ではない

    for prime in primes:
        if prime > math.sqrt(x): break
        if prime == 0: continue
        for non_prime in range(2 * prime, x, prime): primes[non_prime] = 0

    return [prime for prime in primes if prime != 0]

if N == 1 :
    ans = 0
elif N == 2 :
    ans = 1
else :
    ans = 1
    L = primes(N+1)[1:]
    
    for l in L :
        val = l**2 - 2
        
        if val <= N and val in L :
            ans += 2
print(ans)