from lib_prime import get_divisors_count


def euler_179_orig():
    r = 0
    for n in range(2, 10**7):
        if n % 10**5 == 0:
            print(n)
        if get_divisors_count(n) == get_divisors_count(n + 1):
            r += 1
    return r


def euler_179():
    """ Much faster version. """
    upper = 10**7
    ndivs = [1 for _ in range(0, upper + 2)]
    for d in range(2, upper // 2):
        for i in range(d, upper + 2, d):
            ndivs[i] += 1

    r = 0
    for i in range(2, upper + 1):
        if ndivs[i] == ndivs[i + 1]:
            r += 1
    return r


if __name__ == "__main__":
    solution = euler_179()
    print("e179.py: " + str(solution))
    assert(solution == 986262)