def lfff_name(lt):
    """Create mch-filename for icon ctrl run for given leadtime.

    Args:
        lt (int): leadtime

    Returns:
        str: filename of icon output simulation in netcdf, following mch-convention

    """
    hour = int(lt) % 24
    day = (int(lt) - hour) // 24
    remaining_s = round((lt - int(lt)) * 3600)
    sec = int(remaining_s % 60)
    mm = int((remaining_s - sec) / 60)

    return f"lfff{day:02}{hour:02}{mm:02}{sec:02}.nc"