Bug: Type Mismatch in Arithmetic Operation Comparison

The variable "operation" is currently being read is an int. but later compared to string literals ("+". "-". "*","/") which causes mypy to throw type comparison error

<img width="874" height="651" alt="Image" src="https://github.com/user-attachments/assets/a1c296a5-121e-489c-8c5b-6d6dd61336fb" />