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.lang.reflect.Array;
import java.util.*;

public class Main {
    BufferedReader input;
    PrintWriter output;

    Main() {
        try {
            input = new BufferedReader(new FileReader("input.txt"));
            output = new PrintWriter(new FileWriter("output.txt"), true);
            solve();
        } catch (Exception ex) {
//            ex.printStackTrace();
            input = new BufferedReader(new InputStreamReader(System.in));
            output = new PrintWriter(System.out, true);
            solve();
        } finally {
            try {
                input.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            output.close();
        }
    }

    StringTokenizer st;

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

    int nextInt() {
        return Integer.valueOf(nextToken());
    }

    long nextLong() {
        return Long.valueOf(nextToken());
    }

    double nextDouble() {return Double.valueOf(nextToken());}

    void solve() {
        int n = nextInt();
        int s = nextInt();
        int[] a = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = nextInt();
        }
        if (n == 1) {
            output.print(a[0]);
            return;
        }
        if (n == 2) {
            if (s == 1)
                output.print(a[0]+a[1]);
            else
                output.print(a[1]);
            return;
        }
        int max = a[n-1];
        int lf = 0;
        int r = n-1;
        for (int i = r; i >= lf; i--) {
            if (i == lf) continue;
            if ((i-lf+1)/s < 2 && s != 1) {
                s--;
            } else {
                max = Math.max(max, a[i]+a[lf]);
                lf++;
                s--;
            }
        }
        output.print(max);
    }

    class Pair implements Comparable<Pair>{
        String s;
        Double wt;

        public Pair(String s, double wt) {
            this.s = s;
            this.wt = wt;
        }

        @Override
        public int compareTo(Pair o) {
            return o.wt.compareTo(this.wt);
        }

        @Override
        public String toString() {
            return "Pair{" +
                    "s='" + s + '\'' +
                    ", wt=" + wt +
                    '}';
        }
    }

    public static void main(String[] args) {
        new Main();
    }
}