import java.util.*;

public class Solution {

    static Scanner sc = new Scanner(System.in);


    public static int cuttingTime(int N,int K,int[] P){
        if(N==K)return 0;

        int[] dp = new int[N];

        Deque<Integer> dqcost = new LinkedList<>();
        Deque<Integer> dqindex = new LinkedList<>();

        for(int i=0;i<=K;i++) {
            dp[i] = P[i];

            while(!dqcost.isEmpty() && dqcost.getLast()>dp[i]) {
                dqcost.remove();
                dqindex.remove();
            }

            dqcost.add(dp[i]);
            dqindex.add(i);
        }

        for(int i =K+1;i<N;i++) {
            if(!dqindex.isEmpty() && dqindex.getFirst()<i-K-1) {
                dqcost.remove();
                dqindex.remove();
            }

            dp[i] = P[i] + dqcost.getFirst();
            while(!dqcost.isEmpty() && dqcost.getLast()>dp[i]) {
                dqcost.remove();
                dqindex.remove();
            }

            dqcost.add(dp[i]);
            dqindex.add(i);
        }

        int ans = 10000000;

        for(int i=N-K-1;i<N;i++) {
            if(ans > dp[i]) {
                ans = dp[i];
            }
        }

        return ans;
    }

    public static void main(String[] args) {
        int N,K;
        N = sc.nextInt();
        K = sc.nextInt();

        int[] P = new int[N];

        for(int i = 0;i<N;i++) {
            P[i] = sc.nextInt();

        }

        System.out.println(cuttingTime(N,K,P));
    }
}