#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <iomanip>
#include <algorithm>
#include <map>
#include <stack>
#include <queue> 
#include <list>
#include <utility>
#include <fstream>
#include <cstring>
#include <cstdio> 

#define lli long long int
#define M 1000000007 

using namespace std;

lli arr[100000] ;

int main()
{

	lli n, k ;	
	
	cin >> n >> k ;
	
	lli i, j ;
	
	for(i=1;i<=n;i++)
		cin >> arr[i] ; 
	
	lli mi = 999999999, in = -1 ;
	lli sum = 0 ; 
		
	for(i=1;i<=n;i++)
	{
		for(j=i;j<=i+k;j++)
		{
			if(arr[j] <= mi)
			{
				mi = arr[j] ; 
				in = j ; 
			}
		}
		
		//cout << in << endl ;
		
		sum+= arr[in] ; 
		
		i = in + k ; 
		
		mi = 999999999 ;
		
		in = -1 ;
	}
	
	cout << sum << endl ;
	
}