Kevin Sun wants to move his precious collection of n cowbells from Naperthrill to Exeter, where there is actually grass instead of corn. Before moving, he must pack his cowbells into k boxes of a fixed size. In order to keep his collection safe during transportation, he won't place more than two cowbells into a single box. Since Kevin wishes to minimize expenses, he is curious about the smallest size box he can use to pack his entire collection. 

Kevin is a meticulous cowbell collector and knows that the size of his i-th (1 ≤ i ≤ n) cowbell is an integer si. In fact, he keeps his cowbells sorted by size, so si - 1 ≤ si for any i > 1. Also an expert packer, Kevin can fit one or two cowbells into a box of size s if and only if the sum of their sizes does not exceed s. Given this information, help Kevin determine the smallest s for which it is possible to put all of his cowbells into k boxes of size s.

Input

The first line of the input contains two space-separated integers n and k (1 ≤ n ≤ 2·k ≤ 100 000), denoting the number of cowbells and the number of boxes, respectively.

The next line contains n space-separated integers s1, s2, ..., sn (1 ≤ s1 ≤ s2 ≤ ... ≤ sn ≤ 1 000 000), the sizes of Kevin's cowbells. It is guaranteed that the sizes si are given in non-decreasing order.

Output

Print a single integer, the smallest s for which it is possible for Kevin to put all of his cowbells into k boxes of size s.

Examples

Input

2 1
2 5


Output

7


Input

4 3
2 3 5 9


Output

9


Input

3 2
3 5 7


Output

8

Note

In the first sample, Kevin must pack his two cowbells into the same box. 

In the second sample, Kevin can pack together the following sets of cowbells: {2, 3}, {5} and {9}.

In the third sample, the optimal solution is {3, 5} and {7}.

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

public class Main { 		// <- название класса туда
	static class Out{
		private Formatter out;
		final static String EOL="\r\n";
		public Out(PrintStream a) {out=new Formatter(a);}
		public Out(String a) throws FileNotFoundException {out=new Formatter(a);}
		public void close() {out.close();}
		public void print(Object ans) {out.format(String.valueOf(ans));}
		public void println(){out.format(EOL);}
		public void println(Object ans){out.format(String.valueOf(ans)+EOL);}
		public void flush(){out.flush();}
	}
	static boolean IOtypeisFile=false; 	// <- ввод/вывод идёт в качестве файла? (если ввод/вывод файл-true, если консоль-false)
	static String FileInput="C:\\Intel\\a.in", //<- название файла-ввода туда
				  FileOutput="C:\\Intel\\a.out";// <- название файла-вывода туда
	static Scanner in;
	static Out out;
	private static int[] array(int n) {int[] ans=new int[n];for(int i=0;i<n;i++){ans[i]=in.nextInt();}return ans;}
	public static void main(String[] args) {
		if (IOtypeisFile) {
			File f =new File(FileInput);
			try {
				in=new Scanner(f); 
				out=new Out(FileOutput);
			} catch (FileNotFoundException e) {System.err.println(e);}
		} else {
			in=new Scanner(System.in);
			out=new Out(System.out);
		}
		Solution();
		in.close();
		out.close();
	}
	//Код пишут отсюда |
	//				   V
	private static void Solution(){
		int n=in.nextInt(),k=in.nextInt();
		int[] s=array(n);
		int l=0,r=n-1,ans=s[s.length-1];
		for (;2*k>n;k--) {r--;n--;}
		if (r>0) {
			for(;l<r;l++,r--) {ans=Math.max(ans, s[l]+s[r]);}
		}
		out.println(ans);
	}
}