https://leetcode.com/problems/first-bad-version/?envType=study-plan&id=algorithm-i
class Solution:
def firstBadVersion(self, n: int) -> int:
left = 1
right = n
while left < right :
mid = (left+right)//2
if isBadVersion(mid):
right = mid # 2
else :
left = mid + 1
return left