How to get preview image from Youtube link?

This below one should be good enough

https://img.youtube.com/vi/f1qz8vn3XbY/0.jpg

However, there are also links upto 4
https://img.youtube.com/vi/f1qz8vn3XbY/1.jpg

https://img.youtube.com/vi/f1qz8vn3XbY/2.jpg
https://img.youtube.com/vi/f1qz8vn3XbY/3.jpg

references:
https://stackoverflow.com/questions/2068344/how-do-i-get-a-youtube-video-thumbnail-from-the-youtube-api