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