Can you tell me what's wrong in this code?

Question

https://code.sololearn.com/cwLcvqVc3n19/?ref=app

Answer 1

https://code.sololearn.com/c5RKe8JdUe0w/?ref=app

Answer 2

The is no "Null".

Answer 3

1. 'while n == 1' will only be true if user inputs 1. Otherwise, the loop is never executed.
2. 'while s1.size() is not Null' will either run never or forever. s1 doesn't change inside the loop
3. The question doesn't inform what the code should do.