切断圆环链 Cutting Chains

题意翻译

现在有n个圆环，其中可能有些已经连接在一起现在你想拆开一些圆环与其他圆环连接，使得最后所有圆环都在一条串上问至少需要拆开几个圆环 (n≤15) 感谢 @songhn 提供的翻译。

题目描述

[problemUrl]: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=10&page=show_problem&problem=759 [PDF](https://uva.onlinejudge.org/external/8/p818.pdf) ![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA818/9588cba436e36fdf85fd844a054493144c71cd89.png)

输入输出格式

输入格式

![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA818/821cc5792a65cc72d2d0454f5be79a922e908729.png)

输出格式

![](https://cdn.luogu.com.cn/upload/vjudge_pic/UVA818/de0f05a76005d5842d5a31d5c281cf7842612760.png)

输入输出样例

输入样例 #1

5 1 2 2 3 4 5 -1 -1
7 1 2 2 3 3 1 4 5 5 6 6 7 7 4 -1 -1
4 1 2 1 3 1 4 -1 -1
3 1 2 2 3 3 1 -1 -1
3 1 2 2 1 -1 -1
0

输出样例 #1

Set 1: Minimum links to open is 1
Set 2: Minimum links to open is 2
Set 3: Minimum links to open is 1
Set 4: Minimum links to open is 1
Set 5: Minimum links to open is 1