Sum values in two columns, always using first

I am adding two cels (A1 and A2) and showing the result in B2. I want to copy and paste that formula all the way down but it automatically adjusts to A2/A3 then A3/A4 when I would like it to always subtract from A1.

What I have are points standings from an event and want to show the points gap between one person and the leader.