C++ :

#include<iostream>
#include<algorithm>
using namespace std;
const int N = 105;
int a[N],b[N];

int main(){
	int n,r,sum=0;
	cin>>n>>r;
	for (int i=1; i<=n; i++) cin>>a[i];
	sort(a+1,a+n+1);
	for (int i=1; i<=r; i++) b[i]=a[i];
	for (int i=r+1; i<=n; i++) b[i]=b[i-r]+a[i];
	for (int i=1; i<=n; i++) sum+=b[i];
	cout<<sum<<endl;
	return 0;
}