def get_strptime_pattern(s):
    """
    :param s: str
    :return: get strptime pattern

    NOTE: be careful with microseconds. It is not handled properly
    """
    if len(s) > 20:
        raise Exception("Too big string")

    return "%Y%m%d%H%M%S%f"[: int(len(s) - 2)]