主题

3-idiots

Problem Description

King OMeGa catched three men who had been streaking in the street. Looking as idiots though, the three men insisted that it was a kind of performance art, and begged the king to free them. Out of hatred to the real idiots, the king wanted to check if they were lying. The three men were sent to the king's forest, and each of them was asked to pick a branch one after another. If the three branches they bring back can form a triangle, their math ability would save them. Otherwise, they would be sent into jail.

However, the three men were exactly idiots, and what they would do is only to pick the branches randomly. Certainly, they couldn't pick the same branch - but the one with the same length as another is available. Given the lengths of all branches in the forest, determine the probability that they would be saved.

Input

An integer T(T≤100) will exist in the first line of input, indicating the number of test cases.

Each test case begins with the number of branches N(3≤N≤105).

The following line contains N integers a_i (1≤a_i≤105), which denotes the length of each branch, respectively.

Output

Output the probability that their branches can form a triangle, in accuracy of 7 decimal places.

Sample Input

2

4

1 3 3 4

4

2 3 3 4

Sample Output

0.5000000

1.0000000

1. 和为偶数的，多计算了一次自己与自己组合

2. 处理完上面的之后，得到的是排列的个数。如果要拿到组合的个数就还需要/2。

（HDU不让用M_PI，然后只好手写……）