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}.
### TEMPLATE BEGIN

from collections import defaultdict

def read_int():
    return int(raw_input())

def read_ints():
    return (int(x) for x in raw_input().split())

def read_int_list():
    return [int(x) for x in raw_input().split()]

def read_float():
    return float(raw_input())

def read_floats():
    return (float(x) for x in raw_input().split())

def read_float_list():
    return [float(x) for x in raw_input().split()]

def read_list():
    return [x for x in raw_input().split()]

### TEMPLATE END

def count(l, k):
    ret = 0
    curr = 0
    num = 0
    i = 0
    j = len(l)-1
    while i <= j:
        ret += 1
        if i < j and l[i] + l[j] <= k:
            i += 1
            j -= 1
        else:
            i += 1
    return ret

def solve():
    n, k = read_ints()
    l = read_int_list()[::-1]
    left = l[0]
    right = 2 * left
    while left != right:
        mid = (left + right)/2
        if count(l, mid) <= k:
            right = mid
        else:
            left = mid+1
    print left

qq = 1
# qq = 2**30
# qq = read_int()
for _________ in xrange(qq):
    solve()
