It is just a mining spanning tree ( 最小生成树 ) problem, what makes you a little difficult is that you are in a 3D space.
The first line of the input contains the number of test cases in the file. And the first line of each case contains one integer numbers n (0<n<30) specifying the number of the point . The next n lines, each line contains Three Integer Numbers xi, yi and zi, indicating the position of point i.
For each test case, output a line with the answer, which should accurately rounded to two decimals .