using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

class Solution {
    static void Main(String[] args) {
        var arr = Console.ReadLine().Split(' ').Select(s => long.Parse(s)).ToArray();
        n = arr[0];
        k = arr[1];
        costs = Console.ReadLine().Split(' ').Select(s => long.Parse(s)).ToArray();
        
        long result = MinCost(new bool[n], -1);
        
        Console.WriteLine(result);
    }
    
    static long MinCost(bool[] isOff, int lastOff){
        if (isOff.All(c => c)){
            return 0;
        }
        
        long best = long.MaxValue;
        
        for(int i=1; i <= 2*k+1; i++){
            int trial = lastOff + i;
            if(trial < n){
                long curr = costs[trial];
                if (curr < best){
                    curr += MinCost(TurnOff(trial, isOff), trial);
                    best = Math.Min(best, curr);
                }
            }
        }
                
        return best;
    }
    
    static bool TurnsOffAny(int s, bool[] arr){
        for(int i=s; i>=0 && i>=(s-k); i--){
            if (!arr[i]){
                return true;
            }
        }
        
        for(int i=s; i<n && i<=(s+k); i++){
            if(!arr[i]){
                return true;
            }
        }
        
        return false;
    }
    
    static bool[] TurnOff(int s, bool[] prev){
        bool[] result = new bool[n];
        Array.Copy(prev, result, n);
        
        for(int i=s; i>=0 && i>=(s-k); i--){
            result[i] = true;
        }
        
        for(int i=s; i<n && i<=(s+k); i++){
            result[i] = true;
        }
        
        return result;
    }

    static long[] costs;
    static long n;
    static long k;
}