stfih tsfih sftih fstih tfsih ftsih stifh tsifh sitfh istfh tisfh itsfh sfith fsith sifth isfth fisth ifsth tfish ftish tifsh itfsh fitsh iftsh stfhi tsfhi sfthi fsthi tfshi ftshi sthfi tshfi shtfi hstfi thsfi htsfi sfhti fshti shfti hsfti fhsti hfsti tfhsi fthsi thfsi htfsi fhtsi hftsi stihf tsihf sithf isthf tishf itshf sthif tshif shtif hstif thsif htsif sihtf ishtf shitf hsitf ihstf histf tihsf ithsf thisf htisf ihtsf hitsf sfiht fsiht sifht isfht fisht ifsht sfhit fshit shfit hsfit fhsit hfsit sihft ishft shift hsift ihsft hisft fihst ifhst fhist hfist ihfst hifst tfihs ftihs tifhs itfhs fiths ifths tfhis fthis thfis htfis fhtis hftis tihfs ithfs thifs htifs ihtfs hitfs fihts ifhts fhits hfits ihfts hifts
Note: these 'words' (valid or invalid) are all the permutations of the word stfih. These words are obtained by scrambling the letters in stfih.