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.StringTokenizer;

/**
 * Created by Kamil Khadiev on 11.08.2015.
 */
public class khadiev_345_b {
    public static void main(String[] args) throws IOException {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        init(in);
        in.close();
        solve();
        PrintWriter out = new PrintWriter(System.out);
        print(out);
        out.close();

    }
    public static int n, k;
    public static int[] a;
    public static long ans;
    public static int INF = Integer.MAX_VALUE/2;

    private static void init(BufferedReader in) throws IOException {

        StringTokenizer st = new StringTokenizer(in.readLine().trim());
        n =  Integer.parseInt(st.nextToken());
        k =Integer.parseInt(st.nextToken());
        a = new int[n];
        st = new StringTokenizer(in.readLine().trim());
        for (int i = 0; i < n; i++){
            a[i] = Integer.parseInt(st.nextToken());

        }

    }

    private static void solve() {
        ans = 0;
        if (n<=k) ans = a[n-1];
        else {
            int l = n - k;
            if (n - 2*l > 0) {
                ans = a[n - 1];
            }
            for (int i = 0; i < l; i++) {
                if (ans < a[i] +a[2*l-i-1]){
                    ans = a[i] +a[2*l-i-1];
                }
            }
        }

    }

    private static void print(PrintWriter out) throws IOException {
        out.print(ans);
    }
}
