firsts ifrsts frists rfists irfsts rifsts fisrts ifsrts fsirts sfirts isfrts sifrts frsits rfsits fsrits sfrits rsfits srfits irsfts risfts isrfts sirfts rsifts srifts firtss ifrtss fritss rfitss irftss riftss fitrss iftrss ftirss tfirss itfrss tifrss frtiss rftiss ftriss tfriss rtfiss trfiss irtfss ritfss itrfss tirfss rtifss trifss fistrs ifstrs fsitrs sfitrs isftrs siftrs fitsrs iftsrs ftisrs tfisrs itfsrs tifsrs fstirs sftirs ftsirs tfsirs stfirs tsfirs istfrs sitfrs itsfrs tisfrs stifrs tsifrs frstis rfstis fsrtis sfrtis rsftis srftis frtsis rftsis ftrsis tfrsis rtfsis trfsis fstris sftris ftsris tfsris stfris tsfris rstfis srtfis rtsfis trsfis strfis tsrfis irstfs ristfs isrtfs sirtfs rsitfs sritfs irtsfs ritsfs itrsfs tirsfs rtisfs trisfs istrfs sitrfs itsrfs tisrfs stirfs tsirfs rstifs srtifs rtsifs trsifs strifs tsrifs firsst ifrsst frisst rfisst irfsst rifsst fisrst ifsrst fsirst sfirst isfrst sifrst frsist rfsist fsrist sfrist rsfist srfist irsfst risfst isrfst sirfst rsifst srifst firsst ifrsst frisst rfisst irfsst rifsst fisrst ifsrst fsirst sfirst isfrst sifrst frsist rfsist fsrist sfrist rsfist srfist irsfst risfst isrfst sirfst rsifst srifst fissrt ifssrt fsisrt sfisrt isfsrt sifsrt fissrt ifssrt fsisrt sfisrt isfsrt sifsrt fssirt sfsirt fssirt sfsirt ssfirt ssfirt issfrt sisfrt issfrt sisfrt ssifrt ssifrt frssit rfssit fsrsit sfrsit rsfsit srfsit frssit rfssit fsrsit sfrsit rsfsit srfsit fssrit sfsrit fssrit sfsrit ssfrit ssfrit rssfit srsfit rssfit srsfit ssrfit ssrfit irssft rissft isrsft sirsft rsisft srisft irssft rissft isrsft sirsft rsisft srisft issrft sisrft issrft sisrft ssirft ssirft rssift srsift rssift srsift ssrift ssrift firtss ifrtss fritss rfitss irftss riftss fitrss iftrss ftirss tfirss itfrss tifrss frtiss rftiss ftriss tfriss rtfiss trfiss irtfss ritfss itrfss tirfss rtifss trifss firsts ifrsts frists rfists irfsts rifsts fisrts ifsrts fsirts sfirts isfrts sifrts frsits rfsits fsrits sfrits rsfits srfits irsfts risfts isrfts sirfts rsifts srifts fitsrs iftsrs ftisrs tfisrs itfsrs tifsrs fistrs ifstrs fsitrs sfitrs isftrs siftrs ftsirs tfsirs fstirs sftirs tsfirs stfirs itsfrs tisfrs istfrs sitfrs tsifrs stifrs frtsis rftsis ftrsis tfrsis rtfsis trfsis frstis rfstis fsrtis sfrtis rsftis srftis ftsris tfsris fstris sftris tsfris stfris rtsfis trsfis rstfis srtfis tsrfis strfis irtsfs ritsfs itrsfs tirsfs rtisfs trisfs irstfs ristfs isrtfs sirtfs rsitfs sritfs itsrfs tisrfs istrfs sitrfs tsirfs stirfs rtsifs trsifs rstifs srtifs tsrifs strifs fistsr ifstsr fsitsr sfitsr isftsr siftsr fitssr iftssr ftissr tfissr itfssr tifssr fstisr sftisr ftsisr tfsisr stfisr tsfisr istfsr sitfsr itsfsr tisfsr stifsr tsifsr fisstr ifsstr fsistr sfistr isfstr sifstr fisstr ifsstr fsistr sfistr isfstr sifstr fssitr sfsitr fssitr sfsitr ssfitr ssfitr issftr sisftr issftr sisftr ssiftr ssiftr fitssr iftssr ftissr tfissr itfssr tifssr fistsr ifstsr fsitsr sfitsr isftsr siftsr ftsisr tfsisr fstisr sftisr tsfisr stfisr itsfsr tisfsr istfsr sitfsr tsifsr stifsr fstsir sftsir ftssir tfssir stfsir tsfsir fsstir sfstir fsstir sfstir ssftir ssftir ftssir tfssir fstsir sftsir tsfsir stfsir stsfir tssfir sstfir sstfir tssfir stsfir istsfr sitsfr itssfr tissfr stisfr tsisfr isstfr sistfr isstfr sistfr ssitfr ssitfr itssfr tissfr istsfr sitsfr tsisfr stisfr stsifr tssifr sstifr sstifr tssifr stsifr frstsi rfstsi fsrtsi sfrtsi rsftsi srftsi frtssi rftssi ftrssi tfrssi rtfssi trfssi fstrsi sftrsi ftsrsi tfsrsi stfrsi tsfrsi rstfsi srtfsi rtsfsi trsfsi strfsi tsrfsi frssti rfssti fsrsti sfrsti rsfsti srfsti frssti rfssti fsrsti sfrsti rsfsti srfsti fssrti sfsrti fssrti sfsrti ssfrti ssfrti rssfti srsfti rssfti srsfti ssrfti ssrfti frtssi rftssi ftrssi tfrssi rtfssi trfssi frstsi rfstsi fsrtsi sfrtsi rsftsi srftsi ftsrsi tfsrsi fstrsi sftrsi tsfrsi stfrsi rtsfsi trsfsi rstfsi srtfsi tsrfsi strfsi fstsri sftsri ftssri tfssri stfsri tsfsri fsstri sfstri fsstri sfstri ssftri ssftri ftssri tfssri fstsri sftsri tsfsri stfsri stsfri tssfri sstfri sstfri tssfri stsfri rstsfi srtsfi rtssfi trssfi strsfi tsrsfi rsstfi srstfi rsstfi srstfi ssrtfi ssrtfi rtssfi trssfi rstsfi srtsfi tsrsfi strsfi stsrfi tssrfi sstrfi sstrfi tssrfi stsrfi irstsf ristsf isrtsf sirtsf rsitsf sritsf irtssf ritssf itrssf tirssf rtissf trissf istrsf sitrsf itsrsf tisrsf stirsf tsirsf rstisf srtisf rtsisf trsisf strisf tsrisf irsstf risstf isrstf sirstf rsistf sristf irsstf risstf isrstf sirstf rsistf sristf issrtf sisrtf issrtf sisrtf ssirtf ssirtf rssitf srsitf rssitf srsitf ssritf ssritf irtssf ritssf itrssf tirssf rtissf trissf irstsf ristsf isrtsf sirtsf rsitsf sritsf itsrsf tisrsf istrsf sitrsf tsirsf stirsf rtsisf trsisf rstisf srtisf tsrisf strisf istsrf sitsrf itssrf tissrf stisrf tsisrf isstrf sistrf isstrf sistrf ssitrf ssitrf itssrf tissrf istsrf sitsrf tsisrf stisrf stsirf tssirf sstirf sstirf tssirf stsirf rstsif srtsif rtssif trssif strsif tsrsif rsstif srstif rsstif srstif ssrtif ssrtif rtssif trssif rstsif srtsif tsrsif strsif stsrif tssrif sstrif sstrif tssrif stsrif
Note: these 'words' (valid or invalid) are all the permutations of the word firsts. These words are obtained by scrambling the letters in firsts.