ftsio tfsio fstio sftio tsfio stfio ftiso tfiso fitso iftso tifso itfso fsito sfito fisto ifsto sifto isfto tsifo stifo tisfo itsfo sitfo istfo ftsoi tfsoi fstoi sftoi tsfoi stfoi ftosi tfosi fotsi oftsi tofsi otfsi fsoti sfoti fosti ofsti softi osfti tsofi stofi tosfi otsfi sotfi ostfi ftios tfios fitos iftos tifos itfos ftois tfois fotis oftis tofis otfis fiots ifots foits ofits iofts oifts tiofs itofs toifs otifs iotfs oitfs fsiot sfiot fisot ifsot sifot isfot fsoit sfoit fosit ofsit sofit osfit fiost ifost foist ofist iofst oifst sioft isoft soift osift iosft oisft tsiof stiof tisof itsof sitof istof tsoif stoif tosif otsif sotif ostif tiosf itosf toisf otisf iotsf oitsf siotf isotf soitf ositf iostf oistf
Note: these 'words' (valid or invalid) are all the permutations of the word ftsio. These words are obtained by scrambling the letters in ftsio.