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.ArrayList;
import java.util.StringTokenizer;

public class CF604B {
    public static void main(String[] args) {
        FastReader input = new FastReader();
        PrintWriter pw = new PrintWriter(System.out);

        int n = input.nextInt();
        int k = input.nextInt();

        int[] arr = new int[n];


        int maxBell = 0;
        for(int i = 0;i < n;i++){
            arr[i] = input.nextInt();
            maxBell = Math.max(maxBell,arr[i]);
        }

        if(n <= k)
            pw.println(maxBell);
        else{
            ArrayList<Integer> list = new ArrayList<>();

            for(int i = 0;i < arr.length-1;i += 2){
                list.add(arr[i]);
                list.add(arr[i+1]);
                k--;
                n -= 2;
                if(n == k){
                    break;
                }
            }

            int max = Integer.MIN_VALUE;
            int l = 0;
            int r = list.size()-1;
            while (l < r){
                max = Math.max(max,list.get(l)+list.get(r));
                l++;
                r--;
            }
            int left = arr.length - list.size();
            if(left > 0){
                for(int i = arr.length-1;i >= 0;i--){
                    max = Math.max(max,arr[i]);
                    left--;
                    if(left == 0)
                        break;
                }
            }
            pw.println(max);
        }



        // ****If sorting is required, use ArrayList
        pw.flush();
        pw.close();
    }
    static class FastReader
    {
        BufferedReader br;
        StringTokenizer st;

        public FastReader()
        {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

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

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

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

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

        String nextLine()
        {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
}
