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.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Cowbell {

    public static int cow(int[] arr, int boxes) {
        int max = arr[arr.length - 1];
        if (arr.length == boxes) return max;
        int lastIndex = arr.length - 1;
        while (2 * boxes > lastIndex + 1) {
            lastIndex--;
            boxes--;
        }

        for (int i = 0; i <= lastIndex / 2; i++) {
            int curr = arr[i] + arr[lastIndex - i];
            if (i == lastIndex - i) curr = arr[i];
            if (curr > max) max = curr;
        }
        return max;
    }

    public static void main(String[] args) {


        ArrayList<String> arg = new ArrayList<>(); 
        
        try {
            BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); 
            while (arg.size() < 2) {
                arg.add(br.readLine());
            }
            int boxes = Integer.parseInt(arg.get(0).split(" ")[1] );
            String[] sraw = arg.get(1).split(" ");
            int[] s = new int[sraw.length];
            for (int i = 0; i < sraw.length; i++) {
                s[i] = Integer.parseInt(sraw[i]);;
            }
            System.out.println(cow(s,boxes));  
        } catch(IOException io) {
            io.printStackTrace();
        }      
        
    }

}
