def week_cal(cal: str, current_day: int) -> str:
    """Function used to transform a HTML month calendar into a week calendar.

    Args:
        `cal`(str): the html calendar to transform.
        `current_day`(int): the current day to select the current week.

    Returns:
        `str`: the calendar transformed.
    """
    lines = cal.splitlines()
    w = "" # string to store the line of the desired week
    for line in lines: # check each lines for the current day
        if line.__contains__(f">{current_day}<"):
            w = line
    ## build the week calendar ##
    new_cal = lines[0] + "\n" + lines[1] + "\n" + lines[2] + "\n" + w + "\n" + lines[-1]
    return new_cal