rifts irfts rfits frits ifrts firts ritfs irtfs rtifs trifs itrfs tirfs rftis frtis rtfis trfis ftris tfris iftrs fitrs itfrs tifrs ftirs tfirs rifst irfst rfist frist ifrst first risft irsft rsift srift isrft sirft rfsit frsit rsfit srfit fsrit sfrit ifsrt fisrt isfrt sifrt fsirt sfirt ritsf irtsf rtisf trisf itrsf tirsf ristf irstf rsitf sritf isrtf sirtf rtsif trsif rstif srtif tsrif strif itsrf tisrf istrf sitrf tsirf stirf rftsi frtsi rtfsi trfsi ftrsi tfrsi rfsti frsti rsfti srfti fsrti sfrti rtsfi trsfi rstfi srtfi tsrfi strfi ftsri tfsri fstri sftri tsfri stfri iftsr fitsr itfsr tifsr ftisr tfisr ifstr fistr isftr siftr fsitr sfitr itsfr tisfr istfr sitfr tsifr stifr ftsir tfsir fstir sftir tsfir stfir
Note: these 'words' (valid or invalid) are all the permutations of the word rifts. These words are obtained by scrambling the letters in rifts.