https://www.youtube.com/watch?v=ErtPdDUuoYQ&ebc=ANyPxKrCrtgguS90j2TYitzoODgU-O_km9cFkyPAmWaLoFsvAVW2wbqM7NiBKpeJxV9gHUJVkD_kHhPDuBE-VLuMNasiL0_wCw 엠알제거 수준