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

You are given an integer array prices representing the daily price history of a stock, where prices[i] is the stock price on the ith day.
A smooth descent period of a stock consists of one or more contiguous days such that the price on each day is lower than the price on the preceding day by exactly 1. The first day of the period is exempted from this rule.
Return the number of smooth descent periods.
 
Please complete the following python code precisely:
```python
class Solution:
    def getDescentPeriods(self, prices: List[int]) -> int:
```