[Haskell-beginners] shortening code

I have recently started learning haskell, and was trying to write a code for this problem http://www.spoj.pl/problems/KAMIL in haskell. The aim is to write a shortest possible code for the given task. I have previously solved this in c,c++,perl,python.My best was 57 characters using perl. So here's my code in HASKELL: main = interact $ unlines. map (show.foldl (\a x-> if null $ filter (==x) "TDLF" then a else a+a) 1) .lines It is 107 characters [ non white space and newline ]. I was interested in knowing how i could further optimize the size of this code. Thanks in advance. -- Thanks and regards Rizwan A Hudda http://sites.google.com/site/rizwanhudda