@d=split//,'4335443554366887798866555766';$n=int<STDIN>;while($n!=4){p
+rint"$n is ";$n=$n<20?$d[$n]:$d[$n/10+18]+($n%10==0?0:$d[$n%10]);prin
+t"$n.\n";}print"4 is magic.\n";
[download]

125 characters, or 123 if you eliminate that last line break. Looks remarkably like some of the other submissions here, but I didn't cheat and look at anyone else's solutions first - guess there just aren't many ways to do this while keeping it short.

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