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}.
#!/usr/bin/env python3
# 604B_cowbell.py - Codeforces.com/problemset/problem/604/B by Sergey 2015

import unittest
import sys

###############################################################################
# Cowbell Class (Main Program)
###############################################################################


class Cowbell:
    """ Cowbell representation """

    def __init__(self, test_inputs=None):
        """ Default constructor """

        it = iter(test_inputs.split("\n")) if test_inputs else None

        def uinput():
            return next(it) if it else sys.stdin.readline().rstrip()

        # Reading single elements
        [self.n, self.k] = map(int, uinput().split())

        # Reading a single line of multiple elements
        self.nums = list(map(int, uinput().split()))

    def calculate(self):
        """ Main calcualtion function of the class """

        b = self.nums[self.n-self.k:]
        for i in range(self.n-self.k):
            b[i] += self.nums[self.n-self.k-1-i]
        result = max(b)

        return str(result)

###############################################################################
# Unit Tests
###############################################################################


class unitTests(unittest.TestCase):

    def test_single_test(self):
        """ Cowbell class testing """

        # Constructor test
        test = "2 1\n2 5"
        d = Cowbell(test)
        self.assertEqual(d.n, 2)
        self.assertEqual(d.k, 1)
        self.assertEqual(d.nums, [2, 5])

        # Sample test
        self.assertEqual(Cowbell(test).calculate(), "7")

        # Sample test
        test = "4 3\n2 3 5 9"
        self.assertEqual(Cowbell(test).calculate(), "9")

        # Sample test
        test = "3 2\n3 5 7"
        self.assertEqual(Cowbell(test).calculate(), "8")

        # My tests
        test = ""
        # self.assertEqual(Cowbell(test).calculate(), "0")

        # Time limit test
        # self.time_limit_test(5000)

    def time_limit_test(self, nmax):
        """ Timelimit testing """
        import random
        import timeit

        # Random inputs
        test = str(nmax) + " " + str(nmax) + "\n"
        numnums = [str(i) + " " + str(i+1) for i in range(nmax)]
        test += "\n".join(numnums) + "\n"
        nums = [random.randint(1, 10000) for i in range(nmax)]
        test += " ".join(map(str, nums)) + "\n"

        # Run the test
        start = timeit.default_timer()
        d = Cowbell(test)
        calc = timeit.default_timer()
        d.calculate()
        stop = timeit.default_timer()
        print("\nTimelimit Test: " +
              "{0:.3f}s (init {1:.3f}s calc {2:.3f}s)".
              format(stop-start, calc-start, stop-calc))

if __name__ == "__main__":

    # Avoiding recursion limitaions
    sys.setrecursionlimit(100000)

    if sys.argv[-1] == "-ut":
        unittest.main(argv=[" "])

    # Print the result string
    sys.stdout.write(Cowbell().calculate())
