Given an array consisting of `n`

integers, find the contiguous subarray of given length `k`

that has the maximum average value. And you need to output the maximum average value.

**Example 1:**

Input:[1,12,-5,-6,50,3], k = 4Output:12.75Explanation:Maximum average is (12-5-6+50)/4 = 51/4 = 12.75

**Note:**

- 1 <=
`k`

<=`n`

<= 30,000. - Elements of the given array will be in the range [-10,000, 10,000].