I learned square-root decomposition from geeksforgeeks and decided to practice by solving questions. But I am unable to grasp the reason of why my code is making an error

Link to my code

To learn without seeking to blog, I tried to look someone's code and implement it myself. I copied down some code but am unable to look why is my code wrong.

Link to original code

Link to code i wrote copying

Where am I going wrong. Please help me.

Thank you.