Adding and removing circles on the circumference of a circle dynamically

I would appreciate if anyone could help me on this. here is my idea. I am a newbie

A number of circles (a.b,c etc.) drawn on the circumference of a circle X).

When + is pressed, a new circle is added on the circumference which makes thar circle X expand.
When a circle ‘a’ is drap and dropped to a garbage icon, it gets deleted making the circle X shrink in size.

Sankari