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.util.Arrays;
import java.util.LinkedList;

public class CFTest79 {

	static BufferedReader br;
	static LinkedList<String> tokList;
	static {
		br = new BufferedReader(new InputStreamReader(System.in));
		tokList = new LinkedList<String>();
	}

	public static void main(String[] args) throws IOException {
		
		int[]arr=readIntArr();
		int n=arr[0];
		int k=arr[1];
		arr=readIntArr();
		br.close();
		
		if(k>=n){
			System.out.println(arr[n-1]);
		}
		else{
			int sf=n-k;
			int mx=arr[n-1];
			for(int i=0;i<sf;i++){
				mx=Math.max(arr[i]+arr[sf*2-i-1],mx);
			}
			System.out.println(mx);
		}

	}

	static void print(String s){
		System.out.print(s);
	}
	
	static void println(String s){
		System.out.print(s);
	}
	
	static int nextInt() throws IOException {
		return Integer.parseInt(nextTok());
	}

	static long nextLong() throws IOException {
		return Long.parseLong(nextTok());
	}

	static double nextDouble() throws IOException {
		return Double.parseDouble(nextTok());
	}

	static String nextTok() throws IOException {
		if (tokList.size() == 0) {
			String[] strTok = br.readLine().split(" ");
			for (int i = 0; i < strTok.length; i++) {
				tokList.add(strTok[i]);
			}
		}
		return tokList.removeFirst();
	}

	static public String readLine() throws IOException {
		return br.readLine();

	}

	static public long readLong() throws IOException {
		return Long.parseLong(br.readLine());
	}

	static public int readInt() throws IOException {
		return Integer.parseInt(br.readLine());
	}

	static public int[] readIntArr() throws IOException {
		String[] str = br.readLine().split(" ");
		int arr[] = new int[str.length];
		for (int i = 0; i < arr.length; i++)
			arr[i] = Integer.parseInt(str[i]);
		return arr;
	}

	static public double[] readDoubleArr() throws IOException {
		String[] str = br.readLine().split(" ");
		double arr[] = new double[str.length];
		for (int i = 0; i < arr.length; i++)
			arr[i] = Double.parseDouble(str[i]);
		return arr;
	}

	static public long[] readLongArr() throws IOException {
		String[] str = br.readLine().split(" ");
		long arr[] = new long[str.length];
		for (int i = 0; i < arr.length; i++)
			arr[i] = Long.parseLong(str[i]);
		return arr;
	}

	static public double readDouble() throws IOException {
		return Double.parseDouble(br.readLine());
	}
}