rfthi frthi rtfhi trfhi ftrhi tfrhi rfhti frhti rhfti hrfti fhrti hfrti rthfi trhfi rhtfi hrtfi thrfi htrfi fthri tfhri fhtri hftri thfri htfri rftih frtih rtfih trfih ftrih tfrih rfith frith rifth irfth firth ifrth rtifh trifh ritfh irtfh tirfh itrfh ftirh tfirh fitrh iftrh tifrh itfrh rfhit frhit rhfit hrfit fhrit hfrit rfiht friht rifht irfht firht ifrht rhift hrift rihft irhft hirft ihrft fhirt hfirt fihrt ifhrt hifrt ihfrt rthif trhif rhtif hrtif thrif htrif rtihf trihf rithf irthf tirhf itrhf rhitf hritf rihtf irhtf hirtf ihrtf thirf htirf tihrf ithrf hitrf ihtrf fthir tfhir fhtir hftir thfir htfir ftihr tfihr fithr ifthr tifhr itfhr fhitr hfitr fihtr ifhtr hiftr ihftr thifr htifr tihfr ithfr hitfr ihtfr
Note: these 'words' (valid or invalid) are all the permutations of the word rfthi. These words are obtained by scrambling the letters in rfthi.