The Coordinate Plane · Challenge problem

A shape looks like a staircase. Walking around its edge, its corners are $(0, 0)$, $(6, 0)$, $(6, 2)$, $(4, 2)$, $(4, 4)$, $(2, 4)$, $(2, 6)$ and $(0, 6)$, in that order. What is its perimeter, in units?