补题栈
Problem B: 序列
http://xsy.gdgzez.com.cn/JudgeOnline/problem.php?cid=1922&pid=1
Problem C: 交换
http://xsy.gdgzez.com.cn/JudgeOnline/problem.php?cid=1921&pid=2
Problem A: 排列
http://xsy.gdgzez.com.cn/JudgeOnline/problem.php?cid=1920&pid=0
Problem B: ±AB
http://xsy.gdgzez.com.cn/JudgeOnline/problem.php?cid=1920&pid=1
Problem B: Gateau
http://xsy.gdgzez.com.cn/JudgeOnline/problem.php?cid=1916&pid=1
Nim on Towers of Hanoi
https://pe.xiaoyaowudi.com/problem=806
CF1034D Intervals of Intervals