First Bad Version LeetCode solution in Python

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class Solution:
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    def firstBadVersion(self, n: int) -> int:
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        fast, slow = int(n / 2), n
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        diff = abs(fast - slow)
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        while isBadVersion(fast) == isBadVersion(slow) or diff > 1:
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            fast, slow = fast + (-1) ** isBadVersion(fast) * (int(diff / 2) or 1), fast
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            diff = abs(fast - slow)
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        return fast if isBadVersion(fast) else slow