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}.
def score(value,time,wrongAnswer):
    return max(.3*value,(1-time/250.0)*value-(50 * wrongAnswer))

def actualScore():
    times=input().split()
    times=list(map(int,times))
    wrongAnswer=input().split()
    wrongAnswer=list(map(int,wrongAnswer))
    temp=input().split()
    temp=list(map(int,temp))
    total=0
    for problem in range(len(times)):
        total+=score(500*(problem+1),times[problem],wrongAnswer[problem])
    total+=100*int(temp[0])
    total-=50*int(temp[1])
    return int(total)

def maxPair(theList):
    theMax=0
    for index in range(int(len(theList)/2)):
        if theList[index]+theList[len(theList)-1-index]>theMax:
            theMax=theList[index]+theList[len(theList)-1-index]
    return theMax

def cowBox():
    temp=input().split()
    bells=int(temp[0])
    box=int(temp[1])
    temp=input().split()
    sizes=list(map(int,temp))

    if(box>=bells):
        return sizes[len(sizes)-1]
    if(box==bells/2.0):
        return maxPair(sizes)
    else:
        return max(maxPair(sizes[:len(sizes)-(2*box-bells)]),sizes[len(sizes)-1])
print(cowBox())
