Instruction (for Mac):
1. Copy the script (ISO_converter.py) to the folder having the flag image files. (For example: [your downloaded folder]/PNG/16/)
2. Open the terminal app. (/Applications/Utilities/Terminal.app)
3. Use the "cd" command to change to the folder with the script.
4. Run "python ISO_converter.py" to rename the image files. Alternatively, you can run "python ISO_converter.py alpha2" or "python ISO_converter.py numeric" for different ISO formats.