如何强制用户在逗号后输入两位数

I have a form designed to receive a price so the attempted format is XX,XX and X are numbers. I use the pattern ^\d+\,\d\d$ to validate it. It works perfectly (the web app will be used on Firefox Android). The problem is the form allows user to enter a number without digit and the validation works. It's not I except. For example, a user can enter 123 and it will entered in BDD as 123,00.

I would like the user enter 123,00 explicitly. How to do that ? This is a working example :

https://jsfiddle.net/j068zb5e/