YetAnotherRGBSequence

# [[ABC266G] Yet Another RGB Sequence](https://www.luogu.com.cn/problem/AT_abc266_g) 为了方便将 $r,g,b$ 替换为 $a,b,c$。考虑可以将 $a-=k,b-=k$，就变为 $a-k$ 个 $a$，$b-k$ ......