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.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Stack;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.StringTokenizer;
import java.util.TreeSet;
public class cfvc15
{
	static BufferedReader reader;
    static StringTokenizer tokenizer;
    static void init(InputStream input) 
    {
        reader = new BufferedReader( new InputStreamReader(input) );
        tokenizer = new StringTokenizer("");
    }
    static String next() throws IOException
    {
        while ( ! tokenizer.hasMoreTokens() )
        {
            tokenizer = new StringTokenizer(reader.readLine() );
        }
        return tokenizer.nextToken();
    }
 
    static long nextInt() throws IOException 
    {
        return Long.parseLong( next() );
    }
	static PrintWriter writer;
	static void outit(OutputStream outputStream)
	{
		writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
	}
	static void print(Object...objects) {
		for (int i = 0; i < objects.length; i++) 
		{
			if (i != 0)
				writer.print(' ');
			writer.print(objects[i]);
		}
	}
 
	static void println(Object...objects) {
		print(objects);
		writer.println();
	}
 
	static void close() {
		writer.close();
	}
 
	static void flush() {
		writer.flush();
	}
	public static void print_a(long [] a)
    {
    	for(long i : a)
    	{
    		print(i+" ") ;
    	}
    	println() ;
    }
    public static void main(String [] args) throws IOException
    {
    	init(System.in) ;
    	outit(System.out) ;
//    	int t = (int) nextInt() ;
//    	for(int i =0 ; i<t ; i++)
    	output() ;
        flush();
        close();
    }
    static long mod = 1000000007 ;
    static ArrayList<ArrayList<Integer>> ar ;
    static int [] c ;
    public static void output() throws IOException
    {
    	int n = (int) nextInt() ;
    	int k = (int) nextInt() ;
    	long [] a = new long[n] ;
    	for(int i = 0 ; i<n ; i++)
    	{
    		a[i] = (int) nextInt() ;
    	}
    	long ans = 0 ;
    	int br = -1 ;
    	for(int i = 0 ; i<(n+1) ; i+=2)
    	{
    		if((k-i/2)==(n-i))
    		{
    			br = i ;
    			break ;
    		}
//    		ans = Math.max(a[i]+a[i+1],ans) ;
    	}
//    	println(br) ;
    	if(br!=-1)
    	{
    	for(int i = br ; i<n ; i++)
   		{
   			ans = Math.max(a[i],ans) ;
   		}
    	}
    	else
    	{
    		for(int i = 0 ; i<n ; i++)
    		{
    			ans = Math.max(a[i],ans) ;
    		}
    	}
    	for(int i = 0 ; i<br/2 ; i++)
    	{
    		ans = Math.max(ans,a[i]+a[br-1-i]) ;
    	}
    	println(ans) ;
    }
}