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.util.*;
import java.io.*;

public class CodeForces {

    static Pair arr[];
    static char g[][];
   
    public static void main(String[] args) throws IOException {
        Reader.init(System.in);
        int n = Reader.nextInt(), k = Reader.nextInt();
        int x = (n-k) * 2;
        int arr[] = new int[n];
        int max = 0;
        for (int i = 0; i < n; i++) {
            arr[i] = Reader.nextInt();
            max = Math.max(max, arr[i]);
        }
        
        
        for(int i = 0; i < x/2; i++){
            max = Math.max(max, arr[i] + arr[x-1-i]);
        }
        
        System.out.println(max);
    }

    static int dx[] = {1, 0, -1, 0};
    static int dy[] = {0, 1, 0, -1};
    
    static boolean check(int i, int j){
        return i < g.length && i > -1 && j < g[0].length && j > -1;
    }
    
    
}
    class Edge implements Comparable<Edge> {

        int to;
        int from;
        int cost;

        Edge(int a, int b, int c) {
            from = a;
            to = b;
            cost = c;
        }

        @Override
        public int compareTo(Edge t) {
            return t.cost - cost;
        }
    }

    class Pair implements Comparable<Pair> {

        int pos, time;

        Pair(int a, int b) {
            pos = b;
            time = a;
        }

        @Override
        public int compareTo(Pair t) {
            return time - t.time;
        }
    }

    class Reader {

        static BufferedReader reader;
        static StringTokenizer tokenizer;

        public static int pars(String x) {
            int num = 0;
            int i = 0;
            if (x.charAt(0) == '-') {
                i = 1;
            }
            for (; i < x.length(); i++) {
                num = num * 10 + (x.charAt(i) - '0');
            }

            if (x.charAt(0) == '-') {
                return -num;
            }

            return num;
        }

        static void init(InputStream input) {
            reader = new BufferedReader(
                    new InputStreamReader(input));
            tokenizer = new StringTokenizer("");
        }

        static void init(FileReader input) {
            reader = new BufferedReader(input);
            tokenizer = new StringTokenizer("");
        }

        static String next() throws IOException {
            while (!tokenizer.hasMoreTokens()) {
                tokenizer = new StringTokenizer(
                        reader.readLine());
            }
            return tokenizer.nextToken();
        }

        static int nextInt() throws IOException {
            return pars(next());
        }

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

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