import re


def cityscape_structure(filename):
    """
    Parse the structure of Cityscape file names.

    :return: city, seq:0>6, frame:0>6, type, ext
    """
    regex = r"([a-zA-Z]+)_(\d+)_(\d+)_([a-zA-Z0-9]+)_*([a-zA-Z]*.[a-zA-Z]+)"
    elems = re.compile(regex).findall(filename)[0]
    return elems