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.awt.Checkbox;
import java.io.*;
import java.math.*;
import java.util.*;

public class Main {
    static Scanner cin = new Scanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    static BigInteger One = BigInteger.ONE;
    static BigInteger Zero = BigInteger.ZERO;
    static int n,k;
    public static void main(String[] args) throws Exception {
        int[] s = new int[100005];
        n = cin.nextInt(); k = cin.nextInt();
        for(int i = 1; i <= n; i++) s[i] = cin.nextInt();
        long l = 1,r = (long)(1e12);
        long ans = 0;
        while(l <= r) {
            long mid = (l + r) >> 1;
            if(Check(mid,s)) {
                ans = mid;
                r = mid - 1;
            } else {
                l = mid + 1;
            }
        }
        out.print(ans);
        cin.close(); out.close();
    }
    static int[] vis = new int[100005];
    public static boolean Check(long x,int s[]) {
        Arrays.fill(vis, 0);
        int R = n,num = k;
        for(int i = 1; i <= n; i++) {
            if(vis[i] != 0) continue;
            if(num <= 0) return false;
            while(R > i && s[R] + s[i] > x) {
                R--;
            }
            if(R > i) {
                vis[R] = 1;
                R--;
            }
            if(s[i] > x) return false;
            num--;
            //out.println(num);
        }
        return true;
    }
}

