N = int(input())


def sieve(N):
    primes = [True] * (N + 1)
    primes[0] = False
    primes[1] = False
    for i in range(2, N + 1):
        if not primes[i]:
            continue
        for j in range(i * i, N + 1, i):
            primes[j] = False
    return primes


isPrimes = sieve(N)
count = 0
r = 2
while r * r <= N + 2:
    k = r * r - 2
    if isPrimes[k] and isPrimes[r]:

        if k == r:
            count += 1
        else:
            count += 2
    r += 1

print(count)