title: how to return to previous view controllers in current view controller?
body: <p>I want to return to previous view controllers from current one. the situation is like this:
  A,B,C,D are view controllers. A presents B, B presents C, C presents D. i know use delegate can from D to C, C to B, B to A. Now i want to return to A from D directly. How to do this? 
  Any suggestions are appreciated.</p>