Give you N numbers, how many ways to choose 3 numbers A, B, C which satisfy the equation A+B+C=0?

We regard it as two distinct ways if they have different A or different B or different C.

We have multiply cases. For each case:

The first line contains one number: N (0 < N <= 1000)

The second line contains N numbers, Ai, representing the above N numbers(-1e9 < Ai <1e9)

For each case, output one integer, the number of ways.

4
-1 1 0 -1
3
-1 -1 2

12
6

If we use the first -1, we have 6 ways: (-1 1 0), (-1 0 1), (0 1 -1), (0 -1 1), (1 0 -1), (1 -1 0);

And if we use the second -1, we have 6 ways too.

In second example, we consider two -1 is different. So there is 6 ways.