Improve Input Validation

The input validation checks if the input is valid, but it doesn't handle non-integer inputs gracefully. Improve the input validation logic to ensure it properly handles invalid input without crashing the program.

Acceptance Criteria:

The program should clear the input buffer and prompt the user again if the input is not a valid integer within the specified range.

Look for the input validation logic in the codebase, likely in a main function or a specific module handling user input. The task is to modify this logic to clear the input buffer and re-prompt on invalid integer input. Test by running the program and providing non-integer inputs to ensure it handles them gracefully without crashing.

索引モデルが issue の本文から書いたものです。