import random


def make_round():
    step = random.randint(1, 10)
    first_element = random.randint(1, 10)
    a_progression = []
    for i in range(1, 11):
        i_element = str(first_element + (i - 1) * step)
        a_progression.append(i_element)
    secret_element = random.randint(0, 9)
    correct_answer = a_progression[secret_element]
    a_progression[secret_element] = ".."
    question = " ".join(a_progression)
    return question, correct_answer


def rules():
    return 'What number is missing in the progression?'
