In mathematics you don't understand things, you just get used to them.

poj 2888n 种轮换($|G|=n$)第 i 种可以分成长度为 $\frac{n}{\gcd(n,i)}$ 的 $\gcd(n,i)$ 个轮换$\forall g\in G$,$|X^g|...

I see a cotton field, stretching out as far as I can see.The sun, hot and bright, beating down on...