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}.
//package Div334;
import java.io.*;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
public class B
{
    public static void main(String args[])throws IOException
    { 
        InputReader reader = new InputReader(System.in);
        PrintWriter ob=new PrintWriter(System.out);
        int n=reader.readInt();
        int k=reader.readInt();
        int arr[]=new int[n+1];
        for(int i=1;i<=n;i++)
            arr[i]=reader.readInt();
        if(n<=k)
            ob.println(arr[n]);
        else
        {
            int box[]=new int[k+1];
            int val[]=new int[k+1];
            int j=n;
            for(int i=k;i>=1;i--)
            {
                val[i]=arr[j];
                j-=1;
            }
        
            int r=1;
            for(int q=j;q>=1;q--)
                {
                   // System.out.println(val[1]+" "+j+ " "+k+ " "+q);
                    val[r]+=arr[q];
                    r+=1;
                }
            long ans=0;
            for(int i=1;i<=k;i++)
                ans=Math.max(ans, val[i]);
            ob.println(ans);
        }
        ob.close();
    }
 static final class InputReader {
        private final InputStream stream;
        private final byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
 
        public InputReader(InputStream stream) {
            this.stream = stream;
        }
 
        private int read() throws IOException {
            if (curChar >= numChars) {
                curChar = 0;
                numChars = stream.read(buf);
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }
 
        public final int readInt() throws IOException {
            return (int)readLong();
        }
 
        public final long readLong() throws IOException {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
                if (c == -1) throw new IOException();
            }
            boolean negative = false;
            if (c == '-') {
                negative = true;
                c = read();
            }
            long res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return negative ? -res : res;
        }
 
        public final int[] readIntArray(int size) throws IOException {
            int[] array = new int[size];
            for (int i=0; i<size; i++) {
                array[i] = readInt();
            }
            return array;
        }
 
        public final long[] readLongArray(int size) throws IOException {
            long[] array = new long[size];
            for (int i=0; i<size; i++) {
                array[i] = readLong();
            }
            return array;
        }
 
        public final String readString() throws IOException {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                res.append((char)c);
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }
 
        private boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
    }
 
} 