def is_prime(n):
    if n == 1:
        return False
    for i in range(2, int(n ** 0.5) + 1):
        if n % i == 0:
            return False
    return True

def main():
    N = int(input())
    primes = []
    for i in range(1, N + 1):
        if is_prime(i):
            primes.append(i)

    ans = 0
    for prime in primes:
        tmp = (2 + prime) ** 0.5
        if tmp.is_integer() and is_prime(tmp):
            if tmp == 2:
                ans += 1
            else:
                ans += 2


    print(ans)


if __name__ == "__main__":
    main()