I was rated 5 out of 10 for this code

Question

Any feedback for this code of odd even printing using two threads?

I discussed initially and got feedback that it is only worth of 5 out of 10.

Feel free to share your suggestions to improve this code.
https://sololearn.com/compiler-playground/cY6n1J39OmTj/?ref=app

Answer 1

Any point is fine. Code readability, code quality, performance enhancement etc.

One point I got is the functional paradigm and global variables. It could have been avoided

Answer 2

What's the criteria?
Improve in which direction?