//
//  main.cpp
//  101 Hack 42
//
//  Created by Albastroiu Radu on 10/18/16.
//  Copyright © 2016 Albastroiu Radu. All rights reserved.
//

#include<fstream>
#include<string.h>
#include<ctype.h>
#include<iostream>
#include<algorithm>

using namespace std;

long long best[101000];
int main()
{
    int n, k, i,el,j;
    cin >> n >> k;
    for (i = 1; i <= n; i++)
        best[i] = 1LL << 60;
    
    for (i = 1; i <= n; i++)
    {
        cin >> el;
        for(j=i+k; j>=i; j--)
            best[j] = min(best[i-k-1] + el,best[j]);
    }
    
    cout << best[n];
    
    return 0;
}