// Arup Guha
// 12/27/2018
// Solution to 2018 December Gold Problem: Teamwork

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

public class teamwork {
	
	public static void main(String[] args) throws Exception {
		
		// Read input.
		BufferedReader stdin = new BufferedReader(new FileReader("teamwork.in"));
		StringTokenizer tok = new StringTokenizer(stdin.readLine());
		int n = Integer.parseInt(tok.nextToken());
		int k = Integer.parseInt(tok.nextToken());
		int[] vals = new int[n];
		for (int i=0; i<n; i++) 
			vals[i] = Integer.parseInt(stdin.readLine());
		
		int[] dp = new int[n+1];
		dp[0] = 0;
		
		// Solve for best answer ending at i-1.
		for (int i=1; i<=n; i++) {
			
			// Just go back upto k segments and take the best answer.
			int max = vals[i-1];
			for (int len=1; len<=k && i-len>=0; len++) {
				max = Math.max(max, vals[i-len]);
				dp[i] = Math.max(dp[i], max*len + dp[i-len]);
			}
		}
		
		// Output to file.
		PrintWriter out = new PrintWriter(new FileWriter("teamwork.out"));
		out.println(dp[n]);
		out.close();		
		stdin.close();		
	}
}