Number of Smooth Descent Periods of a Stock

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class Solution:
    def getDescentPeriods(self, prices: List[int]) -> int:
        ans = dp = 1
        for i in range(1, len(prices)):
            if prices[i] == prices[i - 1] - 1:
                dp = dp + 1
            else:
                dp = 1
            ans = ans + dp
        return ans