Number of Smooth Descent Periods of a Stock LeetCode solution in Python

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import sys
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class Solution:
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    def getDescentPeriods(self, prices: List[int]) -> int:
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        def calculate(k, ans):
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            if k > 1:
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                ans += ((k - 1) * (k)) // 2
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                # Sum of Natural Numbers
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                return ans
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            else:
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                return ans
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        end = 0
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        start = 0
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        prev = sys.maxsize
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        k = 0
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        ans = 0
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        while end < len(prices):
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            if prev - prices[end] == 1 or prev == sys.maxsize:
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                k += 1
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                prev = prices[end]
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                end += 1
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            else:
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                ans = calculate(k, ans)
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                start = end
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                if end < len(prices):
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                    prev = sys.maxsize
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                k = 0
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        if k > 1:
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            ans = calculate(k, ans)
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        return ans + len(prices)