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.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;

public class B {
    public static void main(String[] args) throws IOException {
        File inputFile = new File("entradaB");
        if (inputFile.exists())
            System.setIn(new FileInputStream(inputFile));
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder out = new StringBuilder();
        String line;
        while ((line = in.readLine()) != null) {
            int[] nk = readInts(line);
            int[] s = readInts(in.readLine());
            // Arrays.sort(s);
            boolean[] used = new boolean[nk[0]];
            int exceded = Math.min(nk[1] * 2 - nk[0], nk[0]);
            int ans = 0;
            for (int i = 0; i < exceded; i++) {
                ans = Math.max(ans, s[nk[0] - i - 1]);
                used[nk[0] - i - 1] = true;
            }
            for (int i = 0; i < (nk[0] - exceded) / 2; i++)
                ans = Math.max(ans, s[i] + s[nk[0] - exceded - i - 1]);
            out.append(ans + "\n");
        }
        System.out.print(out);
    }

    public static int[] readInts(String line) {
        String[] w = line.trim().split("\\s+");
        int[] a = new int[w.length];
        for (int i = 0; i < a.length; i++)
            a[i] = Integer.parseInt(w[i]);
        return a;
    }
}
