RT，建议撤下这题所有不给证明只给结论的题解

• https://www.luogu.com.cn/blog/20090703zjy/solution-sp106
• https://230243.blog.luogu.org/solution-sp106
• https://359951.blog.luogu.org/solution-sp106

顺便捞 hack 贴，希望能一并处理。