CF149D

https://class.51nod.com/Html/Textbook/ChapterIndex.html#textbookId=126&chapterId=336

https://class.51nod.com/Html/Challenge/Problem.html#problemId=1758

https://www.luogu.com.cn/problem/CF149D

sol，3.中应为 \((\dots)(\dots)\)。