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.*;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.PriorityQueue;
import java.util.StringTokenizer;


public class Task_B {
    FastScanner in;
    PrintWriter out;

    public static void main(String[] arg) {
        new Task_B().run();
    }
    static int n;
    static int k;
    static int[] s;
    static boolean[] help;
    public void solve() throws IOException {
    	n = in.nextInt();
    	k = in.nextInt();
    	s = new int[n];
    	for (int i = 0; i < n; i++){
    		s[i] = in.nextInt();
    	}
    	help = new boolean[n];
    	out.print(binS());
    }
   
    static int binS(){
    	int l = 0;
    	int r = Integer.MAX_VALUE;
    	while ((r-l)>1){
    		int mid = (l+r)/2;
    		if (!test(mid)){
    			l = mid;
    		}else{
    			r = mid;
    		}
    	}
    	return r;
    }

    static boolean test(int x){
    	Arrays.fill(help, false);
    	boolean ret = true;;
    	int l = 0;
    	int r = n-1;
    	int count = 0;
    	while ((r-l)>0){
    		if (s[r]+s[l]>x){
    			r--;
    		}else{
    			count++;
    			help[l] = true;
    			help[r] = true;
    			if (count==k){
    				break;
    			}
    			l++;
    			r--;
    		}
    	}
    	for (int i = 0; i < n; i++){
    		if (!help[i] && (s[i]>x || k==count)){
    			ret = false;
    		}else{
    			if (!help[i]){
    				count++;
    			}
    		}
    	}
    	return ret;
    }
    
    
    public void run() {
        try {
            in = new FastScanner(new BufferedReader(new InputStreamReader(System.in)));
            out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));

            solve();

            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    class FastScanner {
        BufferedReader br;
        StringTokenizer st;

        FastScanner(BufferedReader bufferedReader) {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }



    }
}