「co-examination - A」
破壁,组合意义法:五种颜色 $\star,a,b,c,d$。对于 l.h.s.钦定 $k$,在 $3n+k$ 个球中选出 $2n$ 个球染色,在靠左的 $n$ 个球中选 $k$ 个染成 $a$ ...
In mathematics you don't understand things, you just get used to them.
In mathematics you don't understand things, you just get used to them.