package Greedy;

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

/*
 * @author -- rajatgoyal715
 */

public class GreedyFlorist {
    public static void main( String args[] ){
        Scanner in = new Scanner(System.in);
        int N, K;
        N = in.nextInt();
        K = in.nextInt();
        int C[] = new int[N];
        for(int i=0; i<N; i++){
           C[i] = in.nextInt();
        }
        Arrays.sort(C);
        int result = 0;
        int x =1;
        int j=0;
        for(int i=N-1;i>=0;i--){
            result = result + x*C[i];
            j++;
            if(j==K){
                x++;
                j=0;
            }
        }
        System.out.println( result );
    }
}