#include<stdio.h>
int m,n,a[550],r[110];
int main()
{
	scanf("%d %d",&n,&m);
	for(int i=1;i<=n;i++)
	scanf("%d",&a[i]);
	for(int i=1;i<n;i++)
	for(int j=i+1;j<=n;j++)
	if(a[i]>a[j])
	{
		int t=a[i];
		a[i]=a[j];
		a[j]=t;
	}
	int t=1;
	for(int i=1;i<=n;i++)
	{
		if(t==m+1)	t=1;
		a[i]+=r[t];
		r[t]+=a[i];
		t++;
	}
	int s=0;
	for(int i=1;i<=m;i++)
	s+=r[i];
	printf("%d",s);
	return 0;
}
/**************************************************************
	Problem: 1228
	User: admin
	Language: C
	Result: Accepted
	Time:9 ms
	Memory:1148 kb
****************************************************************/