https://m.dcinside.com/board/dngks/124736?recommend=1

https://m.blog.naver.com/PostView.nhn?blogId=2000happy_&logNo=221817215796&proxyReferer=&proxyReferer=https%3A%2F%2Fblog.naver.com%2F2000happy_%2F221817215796


이천특)1차 양성에 2차 음성이면 음성이다