Downgrade from 2 x SQL 2012 Enterprise (Availability Groups) to 1 x SQL 2012 Standard

For one of our SharePoint farms we currently have 2 x SQL 2012 Enterprise servers running setup with Always On - High Availability groups. We would like to downgrade to just 1 x SQL 2012 Standard server.

Question is what is the best process to do the downgrade?

Thanks in advance.