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

public class Solution {

    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 sc = new Scanner(System.in);
        int n = sc.nextInt();
        int k = sc.nextInt();
        int [] arr = new int[n];
        for(int i=0;i<n;i++){
            arr[i] = sc.nextInt();
        }

        System.out.println(solve(arr,n,k,0));
    }

    private static long solve(int[] arr, int n, int k, int i) {
        if(i>=arr.length){
            return 0;
        }

        long ans =Integer.MAX_VALUE;

        for(int a=i;a<=Math.min(arr.length-1,i+k);a++){
            ans = Math.min(arr[a]+solve(arr,n,k,a+k+1),ans);
        }

        return ans;
    }
}