CF571B Minimization

You've got array $ A $ , consisting of $ n $ integers and a positive integer $ k $ . Array $ A $ is indexed by integers from $ 1 $ to $ n $ . You need to permute the array elements so that value  became minimal possible. In particular, it is allowed not to change order of elements at all.

The first line contains two integers $ n,k $ ( $ 2

Print the minimum possible value of the sum described in the statement.

In the first test one of the optimal permutations is $ 1 4 2 $ . In the second test the initial order is optimal. In the third test one of the optimal permutations is $ 2 3 4 4 3 5 $ .