write a go solution for Description:
Marisa comes to pick mushrooms in the Enchanted Forest.

The Enchanted forest can be represented by n points on the X-axis numbered 1 through n. Before Marisa started, her friend, Patchouli, used magic to detect the initial number of mushroom on each point, represented by a_1,a_2,ldots,a_n.

Marisa can start out at any point in the forest on minute 0. Each minute, the followings happen in order:

- She moves from point x to y (|x-y|<=1, possibly y=x).
- She collects all mushrooms on point y.
- A new mushroom appears on each point in the forest.

Note that she cannot collect mushrooms on minute 0.

Now, Marisa wants to know the maximum number of mushrooms she can pick after k minutes.

Input Format:
Each test contains multiple test cases. The first line contains a single integer t (1<=t<=10^4) — the number of test cases. The description of the test cases follows.

The first line of each test case contains two integers n, k (1<=n<=2*10^5, 1<=k<=10^9) — the number of positions with mushrooms and the time Marisa has, respectively.

The second line of each test case contains n integers a_1,a_2,ldots,a_n (1<=a_i<=10^9) — the initial number of mushrooms on point 1,2,ldots,n.

It is guaranteed that the sum of n over all test cases does not exceed 2*10^5.

Output Format:
For each test case, print the maximum number of mushrooms Marisa can pick after k minutes.

Note:
Test case 1:

Marisa can start at x=2. In the first minute, she moves to x=1 and collect 5 mushrooms. The number of mushrooms will be [1,7,2,3,4]. In the second minute, she moves to x=2 and collects 7 mushrooms. The numbers of mushrooms will be [2,1,3,4,5]. After 2 minutes, Marisa collects 12 mushrooms.

It can be shown that it is impossible to collect more than 12 mushrooms.

Test case 2:

This is one of her possible moving path:

2arrow3arrow2arrow1arrow2arrow3arrow4arrow5

It can be shown that it is impossible to collect more than 37 mushrooms.. Output only the code with no comments, explanation, or additional text.