题目：
题解：
# The isBadVersion API is already defined for you.
# def isBadVersion(version: int) -> bool:class Solution:def firstBadVersion(self, n: int) -> int:left, right = 1, nwhile left <= right:mid = left + (right - left) // 2if not isBadVersion(mid):left = mid + 1else:right = mid - 1return left
