import java.io.*;
import java.math.BigInteger;
import java.util.*;
import java.util.Map.Entry;


public class D
{
	String line;
	StringTokenizer inputParser;
	BufferedReader is;
	FileInputStream fstream;
	DataInputStream in;
	
	void openInput(String file)
	{

		if(file==null)is = new BufferedReader(new InputStreamReader(System.in));//stdin
		else
		{
			try{
		
				
			fstream = new FileInputStream(file);
			in = new DataInputStream(fstream);
			is = new BufferedReader(new InputStreamReader(in));
			}catch(Exception e)
			{
				System.err.println(e);
			}
		}

	}
	
	void readNextLine()
	{
		try {
			line = is.readLine();
			if(line!=null)inputParser = new StringTokenizer(line, " ");
			//System.err.println("Input: " + line);
		} catch (IOException e) {
			System.err.println("Unexpected IO ERROR: " + e);
		}	
		
	}
	
	int NextInt()
	{
		String n = inputParser.nextToken();
		int val = Integer.parseInt(n);
		
		//System.out.println("I read this number: " + val);
		return val;
	}
    
    double NextDouble()
    {
            String n = inputParser.nextToken();
            double val = Double.parseDouble(n);
            
            //System.out.println("I read this number: " + val);
            return val;
    }
	
	long NextLong()
    {
            String n = inputParser.nextToken();
            
            long val = Long.parseLong(n);
            
            return val;
    }
	
	String NextString()
	{
		String n = inputParser.nextToken();
		return n;
	}
	
	void closeInput()
	{
		try {
			is.close();
		} catch (IOException e) {
			System.err.println("Unexpected IO ERROR: " + e);
		}
			
	}
	
	
	public static void main(String [] argv)
	{
		String filePath=null;
		if(argv.length>0)filePath=argv[0];
		new D(filePath);
	}
	Integer [] c;
	TreeMap<Integer, Integer> hm;
	HashMap<Integer, Integer> hmr;
	public D(String inputFile)
	{
		
		openInput(inputFile);
		//readNextLine();
		int T=1;//NextInt();
		StringBuilder sb = new StringBuilder();
		
		for(int t=1; t<=T; t++)
		{
			readNextLine();
			int N=NextInt();
			int K=NextInt();
			int [] a = new int[N];
			long [] res = new long[N+1];
			for(int i=0; i<N; i++)
			{
				readNextLine();
				a[i] = NextInt();
			}
			
			for(int i=1; i<=N; i++)
			{
				res[i] = Long.MAX_VALUE-2000000000;
			}
			
			for(int i=0; i<N; i++)
			{
				long min = Long.MAX_VALUE-2000000000;
				for(int j=1; j<=K+1; j++)
					if(i+1>=j)min = Math.min(min, res[i+1-j]);
				for(int j=0; j<=K; j++)
				{
					int id=i+j+1;
					if(id<0||id>N)continue;
					res[id]= Math.min(res[id], min+a[i]);
				}
			}
			
			
			sb.append(res[N]+"\n");
			
			
		}
		System.out.print(sb);
		
		closeInput();		
	}


}