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}.
/*
     * Code Author: Akshay Miterani
     * DA-IICT
     */
    import java.io.*;
import java.math.BigInteger;
import java.util.*;
     
     
    public class ContestMode1 {
     
    	static double eps=(double)1e-6;
    	static long mod=(int)1e9+7;
    	public static void main(String args[]){
    		InputReader in = new InputReader(System.in);
    		OutputStream outputStream = System.out;
    		PrintWriter out = new PrintWriter(outputStream);
    		//----------My Code Starts Here----------
    		int n=in.nextInt();
    		int k=in.nextInt();
    		int s[]=new int[n];
    		for(int i=0;i<n;i++){
    			s[i]=in.nextInt();
    		}
    		int cnt=0,nn=n,kk=k;
    		for(int i=0;i<k;i++){
    			if(nn<=kk)
    				break;
    			nn-=2;
    			kk-=1;
    			cnt++;
    		}
    		int max=s[0];
    		for(int i=0;i<cnt;i++){
    			max=Math.max(max,s[i]+s[2*cnt-1-i]);
    		}
    		for(int i=2*cnt;i<n;i++){
    			max=Math.max(max, s[i]);
    		}
    		System.out.println(max);
    		out.close();
    		//---------------The End------------------
    	}
    	
    	static long modulo(long a,long b,long c) {
    	    long x=1;
    	    	    long y=a;
    	    	    while(b > 0){
    	    	        if(b%2 == 1){
    	    	            x=(x*y)%c;
    	    	        }
    	    	        y = (y*y)%c; // squaring the base
    	    	        b /= 2;
    	    	    }
    	    	    return  x%c;
    	    	}
    	static long gcd(long x, long y)
        {
            long r=0, a, b;
            a = (x > y) ? x : y; // a is greater number
            b = (x < y) ? x : y; // b is smaller number
            r = b;
            while(a % b != 0)
            {
                r = a % b;
                a = b;
                b = r;
            }
            return r;
        }
    	static class Pair implements Comparable<Pair>{
    		long x;
    		long y;
    		int i;
    		Pair(long xx,long yy){
    			x=xx;
    			y=yy;
    		}
    		@Override
    		public int compareTo(Pair o) {
    			if(this.y==o.y)
					return Long.compare((this.x),(o.x));
				else
					return Long.compare((this.y),(o.y));
    		}
    	}
    	
    	static class InputReader {
    	    public BufferedReader reader;
    	    public StringTokenizer tokenizer;
     
    	    public InputReader(InputStream inputstream) {
    	      reader = new BufferedReader(new InputStreamReader(inputstream));
    	      tokenizer = null;
    	    }
    	    
    	    public String nextLine(){
    	    	String fullLine=null;
    	    	while (tokenizer == null || !tokenizer.hasMoreTokens()) {
    	            try {
    	              fullLine=reader.readLine();
    	            } catch (IOException e) {
    	              throw new RuntimeException(e);
    	            }
    	            return fullLine;
    	          }
    	          return fullLine;
    	    }
    		public String next() {
    	      while (tokenizer == null || !tokenizer.hasMoreTokens()) {
    	        try {
    	          tokenizer = new StringTokenizer(reader.readLine());
    	        } catch (IOException e) {
    	          throw new RuntimeException(e);
    	        }
    	      }
    	      return tokenizer.nextToken();
    	    }
    		public long nextLong() {
    		      return Long.parseLong(next());
    		    }
    	    public int nextInt() {
    	      return Integer.parseInt(next());
    	    }
    	  }
    } 