https://hashcode.co.kr/questions/206/%EB%B7%B0%EC%97%90%EC%84%9C-padding%ED%95%98%EA%B3%A0-margin%EC%9D%98-%EC%B0%A8%EC%9D%B4%EA%B0%80-%EB%AD%94%EA%B0%80%EC%9A%94