How to solve Klotski puzzle in minimum number of moves?

Hi guys,

Does anybody know how to write program for finding solution for Klotski puzzles? (http://phil.freehackers.org/klotski/)

Inspired by SICP, I'm trying to learn lisp and put in use some backtracking technique, but have problem with Klotski. Can someone give me some clue or even code???

Thanks in advance!

http://phil.freehackers.org/klotski/