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class Solution:
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    def peakIndexInMountainArray(self, arr: List[int]) -> int:
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        beg = 0
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        end = len(arr) - 1
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        while beg <= end:
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            mid = (beg + end) // 2
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            if arr[mid] < arr[mid + 1]:
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                beg = mid + 1
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            elif arr[mid] > arr[mid + 1]:
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                end = mid - 1
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        return beg