create a DNA String/stair out of layers via expression

hi

i've got a comp with 2x 25 3d  layers.i'd like to create a spiral stair with this layers.

let's say i'd like to have a ring of 5 layers and offset all 25 layers  in the y axis (layer's height)

//variables

ring_layers=5;//

y_offset= slider;

n=thisComp.numLayers;

code position

y_rotation/orientation=point to the middle of the ring

any help appreciated