#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
 
int main() 
{
	int n,k;
	cin>>n>>k;
	vector<int> a(n);
	for(int i = 0; i < n; ++i){
		cin>>a[i];
	}
	sort(a.begin(),a.end());
	int cost = 1;
	int ans = 0;
	for(int  i = n - 1; i >= 0; --i){
		cost = (n - i - 1) / k + 1;
		ans += cost * a[i];
	}
	cout<<ans;
	// your code goes here
	return 0;
}