Well, I don't think that directly helping would be "ethical", but for what it's worth I (and most of the successful coders from what I remember in the fora) did that one with a rather different approach. One helpful trick is to try the examples in the problem (just insert a print "helpful debugging stuff\n" if $n==number_with_known_property; and see if they get classified correctly by your program. Much more fun is number 113, which has a slick mathematical solution, or my methodical number-crunching solution...