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));
    }
}