写数据生成器，对拍。
一边对拍一边静态查错
by 白桦树 @ 2018-12-22 15:05:43
perfect
by 13794531262hj @ 2018-12-22 15:06:27
```void query()```递归去```if```
```void ask()``` ```x=fa(x)```$\to$```x=fa(fx)```
by 重力做功 @ 2019-01-14 00:00:27