def counters(stats):
    """ Count all_sentences all_questions all_questions_with_ans & all_corrects

    :param stats: list(quintet)
    :rtype int, int, int, int
    :return: all_sentences, all_questions, all_questions_with_ans, all_corrects
    """

    # Initialization of counters.
    all_sentences = 0
    all_questions = 0
    all_questions_with_ans = 0
    all_corrects = 0

    # Parse stats and implement the addings.
    for sentences_num, questions_num, questions_with_ans, corrects, acc in stats:
        all_sentences += sentences_num
        all_questions += questions_num
        all_questions_with_ans += questions_with_ans
        all_corrects += corrects

    return all_sentences, all_questions, all_questions_with_ans, all_corrects