Division

Little D is really interested in the theorem of sets recently. There’s a problem that confused him a long time.  
Let T be a set of integers. Let the MIN be the minimum integer in T and MAX be the maximum, then the cost of set T if defined as (MAX – MIN)^2. Now given an integer set S, we want to find out M subsets S1, S2, …, SM of S, such that



and the total cost of each subset is minimal.

The input contains multiple test cases.
In the first line of the input there’s an integer T which is the number of test cases. Then the description of T test cases will be given.
For any test case, the first line contains two integers N (≤ 10,000) and M (≤ 5,000). N is the number of elements in S (may be duplicated). M is the number of subsets that we want to get. In the next line, there will be N integers giving set S.

For each test case, output one line containing exactly one integer, the minimal total cost. Take a look at the sample output for format.

2
3 2
1 2 4
4 2
4 7 10 1

Case 1: 1
Case 2: 18

The answer will fit into a 32-bit signed integer.

2010 ACM-ICPC Multi-University Training Contest（5）——Host by BJTU