def get_histogram(*args):
    """Count repeats by length.

    Parameters
    ----------
    *args : List
        List containing repeat lists.

    Returns
    -------
    hist_dict : Dictionary
        Dictionary containing number of repeats with certain length.

    """

    hist_dict = {}

    for repeat_list in args:

        for repeat in repeat_list:

            rep_num = repeat[2]

            if rep_num not in hist_dict:

                hist_dict[rep_num] = 1

            else:

                hist_dict[rep_num] += 1

    return hist_dict