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.StringTokenizer;

/**
 * Created by WiNDWAY on 4/15/16.
 */

public class Codeforces_round_334_div_2_MoreCowbell {

    public static void main(String[] args) {
        FScanner input = new FScanner();
        out = new PrintWriter(new BufferedOutputStream(System.out), true);
        int[] cowbells = new int[input.nextInt()];
        int boxes = input.nextInt();
        int highest = -1;
        for (int i = 0; i < cowbells.length; i++) {
            cowbells[i] = input.nextInt();
            highest = Math.max(highest, cowbells[i]);
        }
        int start = 0;
        int end = 2 * (cowbells.length - boxes) - 1;
        while (end > start) {
            int startVal = cowbells[start];
            int endVal = cowbells[end];
            highest = Math.max(highest, startVal + endVal);
            start++;
            end--;
        }
        out.println(highest);
        out.close();
    }

    public static int binarySearch(int[] array, int value, int low, int high) {
        if(low >= high) {
            return -1;
        }
        int mid = (low + high) / 2;
        if(array[mid] == value) {
            return mid;
        }
        return array[mid] > value ? binarySearch(array, value, 0, mid) : mid;
    }

    public static PrintWriter out;

    public static class FScanner {
        BufferedReader br;
        StringTokenizer st;

        public FScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        private String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }

        public String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }

    }
}