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}.
/*
 * Code Author: Jayesh Udhani
 * Dhirubhai Ambani Institute of Information and Communication Technology (DA-IICT ,Gandhinagar)
 * 2nd Year ICT BTECH Student
 */
import java.io.*;
import java.util.*;

public class Array {
    public static void main(String args[])
    {
        InputReader in = new InputReader(System.in);
        OutputStream outputStream = System.out;
        PrintWriter out = new PrintWriter(outputStream);
        //----------My Code Starts Here----------
        int n,k,max=Integer.MIN_VALUE,i;
        n=in.nextInt();
        k=in.nextInt();
        int[] a = new int[n];
        for(i=0;i<n;i++)
            a[i]=in.nextInt();
        if(k>=n)
        {
            for(i=0;i<n;i++)
                max=Math.max(max, a[i]);
            System.out.println(max);
        }
        else
        {
            int j;
            for(i=0,j=2*n-2*k-1;i<j;i++,j--)
                max=Math.max(max, a[i]+a[j]);
            for(i=2*n-2*k;i<n;i++)
                max=Math.max(max, a[i]);
            System.out.println(max);
        }

        out.close();
        //---------------The End———————————————————
    }
    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream inputstream) {
            reader = new BufferedReader(new InputStreamReader(inputstream));
            tokenizer = null;
        }

        public String nextLine(){
            String fullLine=null;
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    fullLine=reader.readLine();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
                return fullLine;
            }
            return fullLine;
        }
        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }
        public long nextLong() {
            return Long.parseLong(next());
        }
        public int nextInt() {
            return Integer.parseInt(next());
        }
    }
}
