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.util.*; 
import java.math.*;
import java.io.*;
import java.text.DecimalFormat;
public class Main{

    static int mod=1000000007 ;
    public static void main(String[] args)  throws IOException {
        s.init(System.in);        
        PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
       int n,k;
       n=s.ni();
       k=s.ni();
       int[] size=new int[n];
       for(int i=0;i<n;i++)
            size[i]=s.ni();
        
     
        int l=size[n-1];
        int h=l;
        if(n>1)
            h+=size[n-2];
        
        while(l<h){
            int mid=(l+h)/2;
            int res=count(size,k,mid);
            if(res<0)
                l=mid+1;
            else if(res>=0)
                h=mid;



        }
        out.println(l);

        
        out.close();
    }
    public static int count(int[] size,int k,int box){
        int n=size.length-1;
        int z=0;
        for(int i=n;i>=z;i--){
            if(size[i]+size[z] <=box  && i>z) {
                z++;
                k--;

            }
            else 
                k--;
           
        }
        return k;
    }
    
    public static int gcd(int a,int b){
        if(a%b==0)
            return b;
        else
            return gcd(b,a%b);
    }
        public static class s {
        static BufferedReader reader;
        static StringTokenizer tokenizer;
 
        /** call this method to initialize reader for InputStream */
        static void init(InputStream input) {
            reader = new BufferedReader(
                        new InputStreamReader(input) );
            tokenizer = new StringTokenizer("");
        }   
 
        /** get next word */
        static String ns() throws IOException {
            while ( ! tokenizer.hasMoreTokens() ) {
                //TODO add check for eof if necessary
                tokenizer = new StringTokenizer(
                    reader.readLine() );
            }
            return tokenizer.nextToken();
        }
 
        static int ni() throws IOException {
            return Integer.parseInt( ns() );
        }
    
        static double nd() throws IOException {
            return Double.parseDouble( ns() );
        }
        static long nl() throws IOException {
            return Long.parseLong( ns() );
        }
        
    }
}