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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.util.LinkedList;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author ATailouloute
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        QuickScanner in = new QuickScanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskB solver = new TaskB();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskB {
        public void solve(int testNumber, QuickScanner in, PrintWriter out) {
            int n = in.nextInt();
            int k = in.nextInt();
            long[] a = in.nextLongArray(n);
            Arrays.sort(a);
            a = ArrayUtils.reverse(a);
            LinkedList<Long> lk = new LinkedList<>();
            for (long el : a) {
                lk.addLast(el);
            }
            long[] r = new long[k];
            int p = 0;
            for (int i = 0; i < k && !lk.isEmpty(); i++) {
                r[i] = lk.pollFirst();
            }
            r = ArrayUtils.reverse(r);
            int av = lk.size();
            for (int i = av - 1; i >= 0; i--) {
                r[i] += lk.pollLast();
            }
            out.println(Arrays.stream(r).max().getAsLong());
        }

    }

    static class ArrayUtils {
        public static long[] reverse(long[] array) {
            if (array == null) return null;
            long[] ret = new long[array.length];
            for (int i = 0, j = array.length - 1; i < array.length; i++, j--) {
                ret[i] = array[j];
            }
            return ret;
        }

    }

    static class QuickScanner {
        BufferedReader br;
        StringTokenizer st;
        InputStream is;

        public QuickScanner(InputStream stream) {
            is = stream;
            br = new BufferedReader(new InputStreamReader(stream), 32768);
        }

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

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

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

        public long[] nextLongArray(int len) {
            long[] a = new long[len];
            for (int i = 0; i < len; i++) {
                a[i] = nextLong();
            }
            return a;
        }

    }
}

