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.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class MoreCowbell {
	public int moreCowbell(int[] size, int k) {
		if(k >= size.length) {
			return size[size.length - 1];
		}
		int res = 0;
		int end = size.length - 1;
		while(k * 2 > end + 1) {
			res = Math.max(res, size[end]);
			end--;
			k--;
		}
		int start = 0;
		while(start < end) {
			res = Math.max(res, size[start++] + size[end--]);
		}
		return res;
	}
	public static void main(String[] args) throws FileNotFoundException {
		MoreCowbell solu = new MoreCowbell();
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();    //# of Cowbells
		int k = sc.nextInt();   //# of boxes
		int[] size = new int[n];
		for(int i = 0; i < n; i++) {
			size[i] = sc.nextInt();
		}
		System.out.println(solu.moreCowbell(size, k));

	}

}
