isbff sibff ibsff bisff sbiff bsiff isfbf sifbf ifsbf fisbf sfibf fsibf ibfsf bifsf ifbsf fibsf bfisf fbisf sbfif bsfif sfbif fsbif bfsif fbsif isbff sibff ibsff bisff sbiff bsiff isfbf sifbf ifsbf fisbf sfibf fsibf ibfsf bifsf ifbsf fibsf bfisf fbisf sbfif bsfif sfbif fsbif bfsif fbsif isffb siffb ifsfb fisfb sfifb fsifb isffb siffb ifsfb fisfb sfifb fsifb iffsb fifsb iffsb fifsb ffisb ffisb sffib fsfib sffib fsfib ffsib ffsib ibffs biffs ifbfs fibfs bfifs fbifs ibffs biffs ifbfs fibfs bfifs fbifs iffbs fifbs iffbs fifbs ffibs ffibs bffis fbfis bffis fbfis ffbis ffbis sbffi bsffi sfbfi fsbfi bfsfi fbsfi sbffi bsffi sfbfi fsbfi bfsfi fbsfi sffbi fsfbi sffbi fsfbi ffsbi ffsbi bffsi fbfsi bffsi fbfsi ffbsi ffbsi
Note: these 'words' (valid or invalid) are all the permutations of the word isbff. These words are obtained by scrambling the letters in isbff.