SudhagarS

def reduce(s):
    global value, minimum
    l = len(s)
    minimum = l
    if l == 1:
        value = 1
        return True
    elif l == 2 and s[0] == s[1]:
        value = 2
        return True

SudhagarS

line1=raw_input().split()
N,K,total,completed,Costs=int(line1[0]),int(line1[1]),0,0,[]
for n in raw_input().split():Costs.append(int(n))
Costs.sort(reverse=True)	
friend=[0]*K
for i in range(N):
	friend[completed%K]+=1
	total=total+friend[completed%K]*Costs[i]
	completed+=1
print total