ufrsd fursd urfsd rufsd frusd rfusd ufsrd fusrd usfrd sufrd fsurd sfurd ursfd rusfd usrfd surfd rsufd srufd frsud rfsud fsrud sfrud rsfud srfud ufrds furds urfds rufds fruds rfuds ufdrs fudrs udfrs dufrs fdurs dfurs urdfs rudfs udrfs durfs rdufs drufs frdus rfdus fdrus dfrus rdfus drfus ufsdr fusdr usfdr sufdr fsudr sfudr ufdsr fudsr udfsr dufsr fdusr dfusr usdfr sudfr udsfr dusfr sdufr dsufr fsdur sfdur fdsur dfsur sdfur dsfur ursdf rusdf usrdf surdf rsudf srudf urdsf rudsf udrsf dursf rdusf drusf usdrf sudrf udsrf dusrf sdurf dsurf rsduf srduf rdsuf drsuf sdruf dsruf frsdu rfsdu fsrdu sfrdu rsfdu srfdu frdsu rfdsu fdrsu dfrsu rdfsu drfsu fsdru sfdru fdsru dfsru sdfru dsfru rsdfu srdfu rdsfu drsfu sdrfu dsrfu
Note: these 'words' (valid or invalid) are all the permutations of the word ufrsd. These words are obtained by scrambling the letters in ufrsd.