Is He Gonna Survive? A hero is on his way to the castle to complete his mission.However,he's benn told that the castle is surrounded with a couple of ......
记录被 Assimilation IV never gonna give up 的瞬间。 一看这个 $n \leq 20$，直接状压。然后被去重诈骗了 $114514$ 秒。 因为可以发现最后所有灯都会被点。。。所以其实操作就是一个 $1 \sim n$ 的排列。。。然后直接计算每盏灯的期望和。。。 ......