Please solve the programming task below using a self-contained code snippet in a markdown code block.

You are given a 0-indexed integer array nums. A subarray s of length m is called alternating if:

m is greater than 1.
s1 = s0 + 1.
The 0-indexed subarray s looks like [s0, s1, s0, s1,...,s(m-1) % 2]. In other words, s1 - s0 = 1, s2 - s1 = -1, s3 - s2 = 1, s4 - s3 = -1, and so on up to s[m - 1] - s[m - 2] = (-1)m.

Return the maximum length of all alternating subarrays present in nums or -1 if no such subarray exists.
A subarray is a contiguous non-empty sequence of elements within an array.
 
Please complete the following python code precisely:
```python
class Solution:
    def alternatingSubarray(self, nums: List[int]) -> int:
```