How to implement html5 pattern to validate input that contains specific letters?

I would like to implement a html5 input pattern to validate if input text contains " - (" characters. There can be characters before and after this text.

Did a lot of internet search however couldn't find a pattern which can behave like Contains method of string class.

Furthermore, I couldn't find a documentation to describe all the features of pattern attribute. Please pass the link if you know one.

Any help would be appreciated.

Thank you.