题目大意：给你n个点然后让你求出去掉一条边之后所形成的最小生成树。

比较基础的次小生成树吧。。。先prime一遍求出最小生成树，在dfs求出次小生成树。

Install Air Conditioning

Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 65535/65535 K (Java/Others)
Total Submission(s): 1038 Accepted Submission(s): 240


Problem Description
NJUST carries on the tradition of HaJunGong. NJUST, who keeps up the ”people-Z??http://www.2cto.com/kf/ware/vc/" target="_blank" class="keylink">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"ll spend?
Input The first line of the input contains a single integer T(T ≤ 100), the number of test cases.
For each case, the first line contains two integers n(3 ≤ n ≤ 1000), k(1 ≤ k ≤ 100). n represents n-1 dormitories and one power plant, k represents the cost of high-load wire per meter. n lines followed contains two integers x, y(0 ≤ x, y ≤ 10000000), representing the location of dormitory or power plant. Assume no two locations are the same, and no three locations are on a straight line. The first one is always the location of the power plant.
Output For each case, output the cost, correct to two decimal places.
Sample Input

2

4 2
0 0
1 1
2 0
3 1

4 3
0 0
1 1
1 0
0 1

Sample Output

9.66
9.00

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