import java.util.*;

public class Solution {

    static int getMinimumCost(int numberOfFriends, Integer[] prices) {
        Arrays.sort(prices, Collections.reverseOrder());

        int i = 0;
        int numberOfBoughtFlowers = 0;
        int minimumCost = 0;
        
        while (i < prices.length) {
            for (int j = 0; j < numberOfFriends && i < prices.length; j++) {
                minimumCost += (1 + numberOfBoughtFlowers) * prices[i];
                i++;
            }
            
            numberOfBoughtFlowers++;
        }
        
        return minimumCost;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        final String SPACE = " ";
        String[] amounts = scanner.nextLine().split(SPACE);
        int numberOfFlowers = Integer.parseInt(amounts[0]);
        int numberOfFriends = Integer.parseInt(amounts[1]);

        Integer[] prices = new Integer[numberOfFlowers];
        String[] priceItems = scanner.nextLine().split(SPACE);

        for (int i = 0; i < numberOfFlowers; i++) {
            int price = Integer.parseInt(priceItems[i]);
            prices[i] = price;
        }

        int minimumCost = getMinimumCost(numberOfFriends, prices);
        System.out.println(minimumCost);
        
        scanner.close();
    }
}