#!/bin/python3
import math
import os
import random
import re
import sys
# Complete the getMinimumCost function below.
#my own solution
def getMinimumCost0(k, c):
if k>=len(c):
return sum(c)
s=sorted(c)
n=len(s)//k+1
cost=0
for i in range(n):
m=len(s)
if m<k: #最后个数小于k了
cost+=sum(s)*(i+1)
return cost
cost+=sum(s[m-k:])*(i+1)
s=s[:m-k]
return cost
# a better solution. more concise.
def getMinimumCost(k, flowers):
res = 0
cnt = 0
flowers = sorted(flowers, key=lambda x: -x)#降序排列
for el in flowers:
res += el * (1 + cnt//k)
cnt += 1
return res
if __name__ == '__main__':
fptr = open(os.environ['OUTPUT_PATH'], 'w')
nk = input().split()
n = int(nk[0])
k = int(nk[1])
c = list(map(int, input().rstrip().split()))
minimumCost = getMinimumCost(k, c)
fptr.write(str(minimumCost) + '\n')
fptr.close()