Given a string str, letters of the word "balloon" (7 letters) can be removed in one iteration. Return the number of iterations the (7 letters) can be removed until no such letters forming word "balloon" are present in the final string.
Example:

1. BALLXXOON -> In 1st iteration , the letters can be removed once, leaving XX, hence only 1
2. NOMDOMEJLELABBALLOON -> 2
3. JSDOEJFEH -> 0
4. BALLOON -> 1
5. HBAELSNUO -> 0