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.*;
/*
 * This file was created by ayush in attempt to solve the problem problems
 */
public class main {
    public void solve(int n,int k,int[] sizes, PrintWriter out) {
	int max =0;
	for(int i=0;i<n;i++){
		max =Math.max(max,sizes[i]);
	}

	for(int i=0;i<n-k;i++){
		max = Math.max(max,sizes[i]+sizes[2*(n-k)-i-1]);
	}

	out.println(max);
    }

    public static void main(String[] args) throws IOException {
	
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out);
        int[] nk = IOUtils.readLinearIntArray(in);
	int[] sizes = IOUtils.readLinearIntArray(in);
        Date t1 = new Date();
        main solver = new main();
        solver.solve(nk[0],nk[1],sizes, out);
        out.flush();
        Date t2 = new Date();
        System.err.println(String.format("Your program took %f seconds", (t2.getTime() - t1.getTime()) / 1000.0));
        out.close();
	
		
	
    }

    static class IOUtils {

        public static int[] readIntArray(Scanner in, int size) {
            int[] array = new int[size];
            for (int i = 0; i < size; i++)
                array[i] = in.nextInt();
            return array;
        }

        public static String[] readStringArray(Scanner in, int size) {
            String[] array = new String[size];
            for (int i = 0; i < size; i++)
                array[i] = in.nextLine();
            return array;
        }

        public static int[] readLinearIntArray(Scanner in, int size) {
            //in.nextLine();
            String[] arr = in.nextLine().split(" ");
            int[] array = new int[size];
            for (int i = 0; i < size; i++)
                array[i] = Integer.parseInt(arr[i]);
            return array;
        }

        public static int[] readLinearIntArray(BufferedReader in) throws IOException {
            //in.nextLine();
            String[] arr = in.readLine().split(" ");
            int[] array = new int[arr.length];
            for (int i = 0; i < arr.length; i++)
                array[i] = Integer.parseInt(arr[i]);
            return array;
        }

        public static Double[] readLinearDoubleArray(BufferedReader in) throws IOException {
            //in.nextLine();
            String[] arr = in.readLine().split(" ");
            Double[] array = new Double[arr.length];
            for (int i = 0; i < arr.length; i++)
                array[i] = Double.parseDouble(arr[i]);
            return array;
        }

        public static String[] convert(int[] from) {
            String[] to = new String[from.length];
            for (int i = 0; i < to.length; i++) to[i] = String.valueOf(from[i]);
            return to;
        }

        public static int[] convert(String[] from) {
            int[] to = new int[from.length];
            for (int i = 0; i < to.length; i++) to[i] = Integer.parseInt(from[i]);
            return to;
        }

        public static int[][] read2DIntArray(BufferedReader in, int rows, int columns, String seprator) throws IOException {
            int[][] array = new int[rows][columns];
            for (int i = 0; i < rows; i++) {
                array[i] = convert(in.readLine().split(seprator));
            }
            return array;
        }

        public static String[][] read2DStringArray(BufferedReader in, int rows, int columns, String seprator) throws IOException {
            String[][] array = new String[rows][columns];
            for (int i = 0; i < rows; i++) {
                array[i] = in.readLine().split(seprator);
            }
            return array;
        }
    }


    static class DEBUG {
        public static void DebugInfo(String disp) {
            System.err.println("DEBUG Info: " + disp);
        }

        public static void DebugVariable(String variable, String value) {
            System.err.println("DEBUG Info: " + variable + " => " + value);
        }


        public static void DebugVariable(String variable, int value) {
            System.err.println("DEBUG Info: " + variable + " => " + value);
        }


        public static void DebugVariable(String variable, long value) {
            System.err.println("DEBUG Info: " + variable + " => " + value);
        }

        public static void DebugArray(int[] value) {
            for (int i = 0; i < value.length; i++) {

                System.err.println("DEBUG Info: " + i + " => " + value[i]);
            }
        }

    }

}
