FFT

https://blog.csdn.net/enjoy_pascal/article/details/81478582

https://www.luogu.com.cn/blog/command-block/fft-xue-xi-bi-ji

https://www.cnblogs.com/rvalue/p/7351400.html

https://blog.csdn.net/Flag_z/article/details/99163939

https://www.cnblogs.com/RabbitHu/p/FFT.html