How to get the current frame?

How to get the current frame?

At first its in the starting frame.
What I want to do is when I press Enter gotoAndStop(3);
and again pressing enter key and if its in frame 5 gotoAndStop(5); etc.

So how to know which frame I’m in at the present moment?

One way I did is giving all the keyframes (3, 5, etc) a particular label
and check using ‘currentLabel == 3 ,…etc’. But is there any way to do it without giving it a label by merely using the keyframe numbers?

why does trace(this.frame); returns ‘undefined’?

Please help.
Thank You.