Fix: Improve minimum coin change logic & add doctest
- Removed unnecessary int() conversions to improve efficiency.
- Updated function parameter type (value: str → value: int) to avoid redundant type casting.
- Added try-except handling to prevent ValueError when user input is not a number.
- Implemented testmod() to enable automated doctest verification.
- Fixed issue where input denominations were not sorted in descending order, which previously led to incorrect results.
