useful things

https://www.zhihu.com/tardis/bd/art/460373184

https://mem.ac/oi/algorithm/dynamic-linear-basis/

https://www.luogu.com/article/v7vgqau1

https://www.cnblogs.com/HaHeHyt/p/17316432.html

https://www.luogu.com.cn/training/288387#problems

https://www.luogu.com/article/7cm27uam

https://www.luogu.com.cn/training/401404

https://www.luogu.com/article/wvkngny0