Flowers - greedy

Problem Statement

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 Nspace 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 Nflowers.

Constraints

1≤N,K≤100 
Any ci is not more than 106 
Result is guaranteed to be less than 231

Sample input #00

3 3
2 5 6

Sample output #00

13

Sample input #01

3 2
2 5 6

Sample output #01

15

Explanation : 
Sample Case #00: In this example, all of you should buy one flower each. Hence, you'll have to pay 13 dollars. 
Sample Case #01: Here one of the friend buys first two flowers in decreasing order of their price. So he will pay (0+1)*5 + (1+1)*2 = 9. And other friend will buy the costliest flower of cost 6. So total money need is 9+6=15.

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import java.io.*;
import java.util.*;

public class Solution {

    public static void main(String[] args) throws IOException{
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String s = br.readLine();
        String[] in = s.split(" ");
        int n = Integer.parseInt(in[0]);
        int k = Integer.parseInt(in[1]);
        s = br.readLine();
        String[] tmp = s.split(" ");
        int[] cost = new int[n];
        for(int i = 0 ; i < n ; i++)
            {
            cost[i] = Integer.parseInt(tmp[i]);
        }
        Arrays.sort(cost);
        int index = 0, total = 0, j = 1;
        for(int i = n - 1 ; i >= 0 ; i--)
            {
            if(j > k)
            {    
                j = 1;
                index++;
            }
            total += (index + 1) * cost[i];
            j++;  
        }
        System.out.println(total);
    }
}