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 ContestDiv2 {

	static int n, k;
	static int[] s;

	public static boolean isValid(int size) {
		int no = k;
		int i = 0;
		int j = n - 1;
		while (i <= j) {
			if (i != j && s[i] + s[j] <= size) {
				no--;
				i++;
				j--;
			} else if (s[i] <= size && s[i] >= s[j]) {
				no--;
				i++;
			} else if (s[j] <= size && s[j] >= s[i]) {
				no--;
				j--;
			} else {
				return false;
			}
		}
		return no >= 0;
	}

	public static int binarySearch() {
		int lo = s[s.length - 1];
		int hi = n >= 2 ? (s[s.length - 1] + s[s.length - 2]) : s[s.length - 1];
		int ans = 0;
		while (lo <= hi) {
			int mid = (lo + hi) / 2;
			if (isValid(mid)) {
				ans = mid;
				hi = mid - 1;
			} else {
				lo = mid + 1;
			}
		}
		return ans;
	}

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