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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;

public class Main implements Runnable {

    public static void main(String[] args) {
        new Thread(new Main()).start();
    }

    @Override
    public void run() {
        BufferedReader in = null;

        try {
            in = new BufferedReader(new InputStreamReader(System.in,
                    "ISO-8859-1"));
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }

        try {
            String line = in.readLine();
            String[] part = line.split(" ");
            int bellNumber = Integer.parseInt(part[0]);
            int boxNumber = Integer.parseInt(part[1]);

            line = in.readLine();
            part = line.split(" ");
            long[] bellSize = new long[bellNumber];
            for (int i = 0; i < bellNumber; i++) {
                bellSize[i] = Integer.parseInt(part[i]);
            }

            int n = 2 * boxNumber - bellNumber;
            long max = bellSize[bellNumber - 1];
            for (int i = 1; i <= (bellNumber - n) / 2; i++) {
                max = Math.max(max, bellSize[i - 1]
                        + bellSize[bellNumber - n - i]);
            }
            
            System.out.print(max);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
