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.Scanner;

/**
 * Created by Antonio on 05/12/2015.
 */
public class main {

    static Integer boxes, cowbells;
    static ArrayList<Integer> bellsizes = new ArrayList<Integer>();

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        String line = sc.nextLine();
        String[] tmp = line.split(" ");
        cowbells = Integer.parseInt(tmp[0]);
        boxes = Integer.parseInt(tmp[1]);

        line = sc.nextLine();
        String aux[] = line.split(" ");

        for (String tmp1 : aux)
            bellsizes.add(Integer.parseInt(tmp1));

        if (boxes >= cowbells) {
            System.out.println(bellsizes.get(bellsizes.size() - 1));
        } else {

            Integer bigger = bellsizes.get(bellsizes.size() - 1);
            for (int i = 0; i < cowbells - boxes; i++){
                if(bigger < (bellsizes.get(i) + bellsizes.get(2 * (cowbells - boxes) - i - 1))){
                    //System.out.println(bigger + "  "+(bellsizes.get(i) + bellsizes.get(2 * (cowbells - boxes) - i - 1)));
                    bigger = (bellsizes.get(i) + bellsizes.get(2 * (cowbells - boxes) - i - 1));
                }
            }

            System.out.println(bigger);
        }
    }
}
//