哦，还有一点，无解输出`-1`
by songyuchen @ 2018-07-06 17:43:31
膜拜
$\color{red}da\ \color{black}l\ \color{blue}ao$
by txr20050504 @ 2018-07-19 22:03:01
@[chen_zhe](/space/show?uid=8457)
by chdy @ 2019-08-09 17:17:37