#include<iostream>
#include<vector>
#include<algorithm>
#include<cstdio>
using namespace std;
int main()
{
	long long int a,n,k;
	cin>>n>>k;
	vector <long long int> v;
	for(int i=0;i<n;i++)
	{
		cin>>a;
		v.push_back(a);
	}
	long int x=k,cost=0;
	sort(v.begin(),v.end());
	while(k)
	{
		if(n<k)
		{
			cout<<v[0];
			break;
		}
		else if(n<=2*k+1)
		{
			if(n%2==0)
			{
				cout<<v[n/2];
			}
			else
			cout<<v[n/2+1];
			break;
		}
		else
		{
			cost+=v[x];
			if(x>n)
			{
				cout<<cost+v[x+1];
				break;
			}
			x+=2*k+1;
		}
	}
}