def firstBadVersion(self, n):
    l = 0
    r = n
    while l<r:
        m = (l + r)//2
        print(l,m,r)
        if(isBadVersion(m)):
            r = m
            if(r == l + 1):
                return m
        else:
            l = m
            if(r == l + 1):
                return l + 1
    return l