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.*;
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////////   MMMM          MMMM    AAAAAAAAAAAAAAAAA  RRRRRRRRRR       EEEEEEEEEEEEE  DDDDDDDDD       /////////
////////   MMMMMM      MMMMMM    AAAAAAAAAAAAAAAAA  RRRR     RRR     EEEEEEEEEEEEE  DDD     DDD     /////////
////////   MMMM MMM  MMM MMMM    AAAA         AAAA  RRRR      RRR    EEEEE          DDD      DDD    /////////
////////   MMMM  MMMMM   MMMM    AAAA         AAAA  RRRR       RRR   EEEEE          DDD       DDD   /////////
////////   MMMM          MMMM    AAAA         AAAA  RRRR      RRR    EEEEE          DDD        DDD  /////////
////////   MMMM          MMMM    AAAA         AAAA  RRRR     RRR     EEEEEEEEEEE    DDD         DDD /////////
////////   MMMM          MMMM    AAAAAAAAAAAAAAAAA  RRRRRRRRRR       EEEEEEEEEEE    DDD         DDD /////////
////////   MMMM          MMMM    AAAAAAAAAAAAAAAAA  RRRR    RRR      EEEEE          DDD        DDD  /////////
////////   MMMM          MMMM    AAAA         AAAA  RRRR     RRR     EEEEE          DDD      DDD    /////////
////////   MMMM          MMMM    AAAA         AAAA  RRRR      RRR    EEEEEEEEEEEEE  DDD    DDD      /////////
////////   MMMM          MMMM    AAAA         AAAA  RRRR       RRR   EEEEEEEEEEEEE  DDDDDDDDD       /////////
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public class MoreCowbell {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);
        int n = sc.nextInt(); int k = sc.nextInt();
        int[] arr = new int[n];
        int max = 0;
        for(int i = 0; i<n; i++){
            arr[i] = sc.nextInt();
        }
        int[] arr2 = new int[k];
        for(int i = 0; i<k && i<arr.length; i++){
            arr2[i] = arr[n-1-i];
        }
        for(int i = 0; i<n-k; i++){
            arr2[k-1-i] = arr2[k-1-i] + arr[n-k-1-i];
        }
        for(int i = 0; i<arr2.length; i++){
            max = Math.max(max, arr2[i]);
        }
        out.println(max);
        out.flush();

    }

    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream system) {
            br = new BufferedReader(new InputStreamReader(system));
        }

        public Scanner(String file) throws Exception {
            br = new BufferedReader(new FileReader(file));
        }

        public String next() throws IOException {
            while (st == null || !st.hasMoreTokens()) st = new StringTokenizer(br.readLine());
            return st.nextToken();
        }

        public String nextLine() throws IOException {
            return br.readLine();
        }

        public int nextInt() throws IOException {
            return Integer.parseInt(next());
        }

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

        public char nextChar() throws IOException {
            return next().charAt(0);
        }

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

        public boolean ready() throws IOException {
            return br.ready();
        }

        public void waitForInput() throws InterruptedException {
            Thread.sleep(3000);
        }
    }
}