还有这几题，一起降难度吧

https://www.luogu.com.cn/problem/P1342

https://www.luogu.com.cn/problem/P1629

https://www.luogu.com.cn/problem/P1821

https://www.luogu.com.cn/problem/SP50

https://www.luogu.com.cn/problem/UVA721

建议全部改成黄题