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.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.io.*;
import java.util.*;

public class Queries {
	
	public static void main(String args[]) {
		MyScanner in = new MyScanner();
		int size = in.nextInt();
		int k = in.nextInt();
		int[] arr = new int[size];
		for (int i = 0; i < size; i++) {
		    arr[i] = in.nextInt();
		}
		cowbell(arr, size, k);
	}
	
	static void cowbell(int[] arr,int n, int k) {
		int ans = arr[n - 1];
		int end = n - 1;
		while (k << 1 > end + 1 && end >= 0) {
			end--;
			k--;
		}
		int start = 0;
		while (end > start) {
			ans = Math.max(ans, arr[start] + arr[end]);
			end--;
			start++;
		}
		System.out.println(ans);
	}
	
	static void heapSort(int[] arr) {
		makeHeap(arr);
		int len = arr.length - 1;
		int max;
		for (int i = 0; i < arr.length; i++) {
			max = arr[0];
			arr[0] = arr[len];
			arr[len] = max;
			len--;
			bubbleDown(arr, 0, len);
		}
	}
	
	static void makeHeap(int[] arr) {
		for (int i = arr.length - 1; i >= 0; i--) {
			bubbleDown(arr, i, arr.length - 1);
		}
	}
	static void bubbleDown(int[] arr, int pos, int len) {
		if (pos * 2 + 1 > len) {
			return;
		}
		int cur = arr[pos];
		int leftChild = arr[pos * 2 + 1];
		int rightChild = (pos * 2 + 2) > len ? Integer.MIN_VALUE : arr[pos * 2 + 2];
		int max = Math.max(Math.max(cur, leftChild), rightChild);
		if (max == leftChild) {
			arr[pos] = leftChild;
			arr[pos * 2 + 1] = cur;
			bubbleDown(arr, pos * 2 + 1, len);
		} else if (max == rightChild) {
			arr[pos] = rightChild;
			arr[pos * 2 + 2] = cur;
			bubbleDown(arr, pos * 2 + 2, len);
		}
	}
	
	public static class MyScanner {
      BufferedReader br;
      StringTokenizer st;
 
      public MyScanner() {
         br = new BufferedReader(new InputStreamReader(System.in));
      }
 
      String next() {
          while (st == null || !st.hasMoreElements()) {
              try {
                  st = new StringTokenizer(br.readLine());
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }
          return st.nextToken();
      }
 
      int nextInt() {
          return Integer.parseInt(next());
      }
 
      long nextLong() {
          return Long.parseLong(next());
      }
 
      double nextDouble() {
          return Double.parseDouble(next());
      }
 
      String nextLine(){
          String str = "";
	  try {
	     str = br.readLine();
	  } catch (IOException e) {
	     e.printStackTrace();
	  }
	  return str;
      }

   }
}