Pick from both sides!

Given an integer array A of size N.

You have to pick exactly B elements from either left or right end of the array A to get the maximum sum.

Find and return this maximum possible sum.

NOTE: Suppose B = 4 and array A contains 10 elements then

• You can pick the first four elements or can pick the last four elements or can pick 1 from the front and 3 from the back etc. you need to return the maximum possible sum of elements you can pick.

1 <= N <= 10⁵

1 <= B <= N

-10³ <= A[i] <= 10³

First argument is an integer array A.

Second argument is an integer B.

Return an integer denoting the maximum possible sum of elements you picked.

Input 1:

 A = [5, -2, 3 , 1, 2]
 B = 3

Input 2:

 A = [1, 2]
 B = 1

Output 1:

 8

Output 2:

 2

Explanation 1:

 Pick element 5 from front and element (1, 2) from back so we get 5 + 1 + 2 = 8

Explanation 2:

 Pick element 2 from end as this is the maximum we can get