//zm.qz1z.com:2501
#include <bits/stdc++.h>
using namespace std;
int main(){
	int n,r,h=0,a[1001]={},b[1001]={};
	cin>>n>>r;
	for(int i=0;i<n;i++) cin>>a[i];
	sort(a,a+n);
	for(int i=0;i<n;i++){
		sort(b,b+r);
		h+=b[0]+a[i];
		b[0]+=a[i];
	}
	cout<<h;
}
/**************************************************************
	Problem: 1228
	User: wangyiyang
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2076 kb
****************************************************************/