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.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.Scanner;

/**
 * Created by slycer on 10/15/15.
 */
public class P2_1 {

    public static void main ( String [] args ) throws IOException {
        BufferedReader reader = new BufferedReader ( new InputStreamReader( System.in ) );
        String [] aux = reader.readLine().split( " " );
        int n = Integer.valueOf(aux[0]);
        int cutii  = Integer.valueOf( aux[1] );

        aux = reader.readLine().split( " " );
        LinkedList<Integer> data = new LinkedList<Integer>();
        for ( int i=0; i<n; i++ ){
            data.push(  Integer.valueOf( aux[i] ) );
        }

        int sol = 0; // dimensiunea maxima a cutii

        while ( 2 * cutii > data.size() && data.size() > 0  ){
            cutii--;
            int last = data.pop();
            sol = Math.max( last, sol );
        }

        if ( data.size() == 1 ){
            sol = Math.max( sol, data.pollLast() );
        }
        while ( data.size() >=2 ){
            sol = Math.max( sol, data.pollFirst() + data.pollLast() );
        }

        System.out.println( sol );
    }


}
