Answer
Inverse action: exit the room.
Work Step by Step
In loose terms,
let f(being outside)=get inside (the room)
We want the inverse to be defined on being inside (the room)
g(being inside )=getting outside
So,
g(f (being outside)=being outside
and
f(g( being inside )= being inside
[ f(g(x))=x and g(f(x))=x ]
Inverse action: exit the room.
