content: import java.io.*;
  import java.math.*;
  import java.security.*;
  import java.text.*;
  import java.util.*;
  import java.util.concurrent.*;
  import java.util.regex.*;
  
  public class Solution {
  
    // Complete the getMinimumCost function below.
    static int getMinimumCost(int k, int[] c) {
      Arrays.sort(c);
      int cost = 0;
      int counter = 1;
      for (int i = c.length - 1; i >= 0; counter++) {
        for (int j = 0; j < k && i >= 0; j++, i--) {
          cost += c[i] * counter;
        }
      }
  
      return cost;
  
    }
  
    private static final Scanner scanner = new Scanner(System.in);
  
    public static void main(String[] args) throws IOException {
      BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));
  
      String[] nk = scanner.nextLine().split(" ");
  
      int n = Integer.parseInt(nk[0]);
  
      int k = Integer.parseInt(nk[1]);
  
      int[] c = new int[n];
  
      String[] cItems = scanner.nextLine().split(" ");
      scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");
  
      for (int i = 0; i < n; i++) {
        int cItem = Integer.parseInt(cItems[i]);
        c[i] = cItem;
      }
  
      int minimumCost = getMinimumCost(k, c);
  
      bufferedWriter.write(String.valueOf(minimumCost));
      bufferedWriter.newLine();
  
      bufferedWriter.close();
  
      scanner.close();
    }
  }
  