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

public class Solution {
    public static void main(String[] args) {
        PrintWriter output = new PrintWriter(System.out);
        new Solution().processInput(new Scanner(System.in), output);
        output.flush();
    }

    public void processInput(Scanner in, PrintWriter output) {
        int n = in.nextInt(); //
        int k = in.nextInt();
        int[] costs = new int[n];
        for (int i = 0; i < n; i++) {
            costs[i] = in.nextInt();
            
        }
        output.println(minCost(n, k, costs));
    }

    private long minCost(int n, int k, int[] costs) {
        boolean[] on = new boolean[n];

        long cost = 0;

        for (int i = 0; i < n;) {
            int minCost = Integer.MAX_VALUE;
            int minIndex = 0;
            for (int j = i; j <= i + k && j<n; j++) {
                if (costs[j] <= minCost) {
                    minCost = costs[j];
                    minIndex = j;
                }
            }
            cost += minCost;
            i = minIndex + k + 1;
        }
        return cost;
    }
}