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.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;

/**
 * http://codeforces.com/problemset/problem/604/B
 * */
public class MoreCowbell {

	static long minSize(int[] a, int nBoxes) {
		long s = 0;		
		for (int v : a) s += v;
		long lo = 0;
		long hi = s;
		while (lo < hi) {
			long boxSize = lo + (hi-lo)/2;
			if (can(boxSize, a, nBoxes)) {
				hi = boxSize;
			} else {
				lo = boxSize+1;
			}
		}
		return lo;
	}
	
	static boolean can(long boxSize, int[] a, int nBoxes) {
		int l = 0;
		int r = a.length - 1;
		int nb = 0;
		while (l <= r) {
			if (a[l] > boxSize || a[r] > boxSize) return false;
			if (a[l] + a[r] <= boxSize) {
				++ l;
				-- r;
				++ nb;
			} else {
				++ nb;
				-- r;
			}						
		}
		return nb <= nBoxes;
	}

	public static void main(String[] args) throws IOException {
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));			
		StringTokenizer st = new StringTokenizer(in.readLine());		
		int n = Integer.parseInt(st.nextToken());
		int k = Integer.parseInt(st.nextToken());
		int[] a = new int[n];
		st = new StringTokenizer(in.readLine());
		for(int i = 0; i < n; ++ i) {
			a[i] = Integer.parseInt(st.nextToken());
		}
		out.println(minSize(a, k));
		out.close();
	}
	
}
