import java.io.*;
import java.util.*;

public class Solution {
    
    public static long turn(int start,int end ,long [] cost,int k)
	{
		
        
        if(end<start)
            return 0;
            
		if(start==end)
		{
			return cost[start];
		}
        
		
		
		
		long sum=999999999;
		for(int i=start;i<=end;i++)
		{
			
			int left=i-k;
			int right=i+k;
			
			long cost1=0;
			long cost2=0;
			
		
				
			
			
			cost1=turn(start,left-1,cost,k);
            
             //System.out.println("right+! "+right +" end "+end  );
			 cost2=turn(right+1,end,cost,k);
            
            //System.out.println("left "+cost1 +" right "+cost2  +" med "+cost[i]);
			long tcost=cost1+cost2+cost[i];
			if(tcost<sum)
				sum=tcost;
			//  System.out.println("tcost "+ tcost +"sum "+sum );
			
			
			
		}
		
		return sum;
		
		
		
	}
	

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        
        	
		Scanner s=new Scanner(System.in);
		int n=s.nextInt();
		int k=s.nextInt();
        long [] cost=new long[n];
        boolean [] state=new boolean[n];
        
        
        for(int i=0;i<n;i++)
        {
            cost[i]=s.nextLong();
            state[i]=true;
            
        }
        
        
        
        System.out.println(turn(0,n-1,cost,k));
        
    }
}