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.io.PrintWriter;
import java.util.Comparator;
import java.util.PriorityQueue;

public class Ltower
{
    private long[] Heap;
    private int size;
    private int maxsize;
 
    private static final int FRONT = 1;
 
    public Ltower(int maxsize)
    {
        this.maxsize = maxsize;
        this.size = 0;
        Heap = new long[this.maxsize + 1];
        Heap[0] = Integer.MIN_VALUE;
    }
 
    private int parent(int pos)
    {
        return pos / 2;
    }
 
    private int leftChild(int pos)
    {
        return (2 * pos);
    }
 
    private int rightChild(int pos)
    {
        return (2 * pos) + 1;
    }
 
    private boolean isLeaf(int pos)
    {
        if (pos >=  (size / 2)  &&  pos <= size)
        {
            return true;
        }
        return false;
    }
 
    private void swap(int fpos,int spos)
    {
        long tmp;
        tmp = Heap[fpos];
        Heap[fpos] = Heap[spos];
        Heap[spos] = tmp;
    }
 
    private void maxHeapify(int pos)
    {
        if (!isLeaf(pos))
        { 
            if ( Heap[pos] > Heap[leftChild(pos)]  || Heap[pos] > Heap[rightChild(pos)])
            {
                if (Heap[leftChild(pos)] < Heap[rightChild(pos)])
                {
                    swap(pos, leftChild(pos));
                    maxHeapify(leftChild(pos));
                }else
                {
                    swap(pos, rightChild(pos));
                    maxHeapify(rightChild(pos));
                }
            }
        }
    }
 
    public void insert(long element)
    {
        Heap[++size] = element;
        int current = size;
 
        while(Heap[current] < Heap[parent(current)])
        {
            swap(current,parent(current));
            current = parent(current);
        }   
    }
 
    public void print()
    {
        for (int i = 1; i <= size / 2; i++ )
        {
            System.out.print(" PARENT : " + Heap[i] + " LEFT CHILD : " + Heap[2*i]
                  + " RIGHT CHILD :" + Heap[2 * i  + 1]);
            System.out.println();
        }
    }
 
    public void maxHeap()
    {
        for (int pos = (size / 2); pos >= 1; pos--)
        {
            maxHeapify(pos);
        }
    }
 
    public long remove()
    {
        long popped = Heap[FRONT];
        Heap[FRONT] = Heap[size--]; 
        maxHeapify(FRONT);
        return popped;
    }
 
    public static void main(String...arg) throws Exception
    {
        BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out, true);
        
        String s[]=in.readLine().split(" ");
        int n = Integer.parseInt(s[0]);
        int k = Integer.parseInt(s[1]);
        
//      PriorityQueue<Long> pq = new PriorityQueue<>(10, new Comparator<Long>() {
//
//          @Override
//          public int compare(Long o1, Long o2) {
//              // TODO Auto-generated method stub
//              return o1.compareTo(o2);
//          }
//      });
//      
        
        
//       System.out.println("The Max Heap is ");
//          Ltower maxHeap = new Ltower(n);
        s = in.readLine().split(" ");
        if(k>=n)
            pw.println(s[n-1]);
        else{
        long arr[]= new long[n];
        int i=0;
        while(i<n){
            arr[i] = Long.parseLong(s[i]);
    
            i++;
        }
        
        
        
        int end = 2*(n-k);
        long ans =arr[n-1];
        for (i = 0; i < end/2; i++)
        {
            ans = Math.max(ans, arr[i] + arr[end - i - 1]);
        }

        pw.println(ans);
       
        }
    }
}