[Haskell-beginners] Question about problem "KAMIL" from SPOJ

Hi, I'm trying to solve problem "KAMIL" on SPOJ site The target is to write as small as possible code. My first solution was: main=interact$unlines.map(show.(2^).length.filter(`elem`"TDLF")).lines This code = 70 bytes and it accepted on SPOJ My second solution was: main=getLine>>=print.(2^).length.filter(`elem`"TDLF")>>main This code = 60 bytes, but i get Run-Time error on SPOJ I don't understand how this code can create RTE? Please help me Nadav