You and your K-1 friends want to buy N flowers. Flower number i has cost ci. Unfortunately the
seller does not want just one customer to buy a lot of flowers, so he tries to change the price
of flowers for customers who have already bought some flowers. More precisely, if a customer
has already bought x flowers, he should pay (x+1)*ci dollars to buy flower number i.
You and your K-1 friends want to buy all N flowers in such a way that you spend the least
amount of money. You can buy the flowers in any order.

Input:

The first line of input contains two integers N and K (K <= N). The next line contains N space separated positive integers c1,c2,...,cN.

Output:

Print the minimum amount of money you (and your friends) have to pay in order to buy all N flowers.

Sample input :

3 3
2 5 6

Sample output :

13

Explanation :
In this example, all of you should buy one flower each. Hence, you'll have to pay 13 dollars.

Constraint :

1 <= N, K  <= 100
Any ci is not more than 1,000,000