https://programist.tistory.com/entry/C-%EC%96%B8%EC%96%B4-%EB%AA%A8%EB%93%A0-%ED%8F%AC%EC%9D%B8%ED%84%B0-%EB%B3%80%EC%88%98-%EC%9E%90%EB%A3%8C%ED%98%95%EC%9D%B4-%EB%98%91%EA%B0%99%EC%9D%80-%ED%81%AC%EA%B8%B0%EB%A5%BC-%EA%B0%80%EC%A7%80%EB%8A%94-%EC%9D%B4%EC%9C%A0
