duplicateMovieClip question.need some help

1

i have this script on a button:

on (release) {
	kast0.duplicateMovieClip("kast"+(num+1), 0);
	this["kast"+(num+1)]._x = kast0._x+((num+1)*15);
	this["kast"+(num+1)]._y = kast0._y;
	num++;
}

and this in frame one:

num = 0;

“kast0” is a MC, that i want to duplicate(with every click), so there would be many of those in a row. but that script “ereases” the “kast1” if it creates “kast2”
currently i have my fla with only one frame and there is no other actions.

i have my fla here to: myFLA