didst iddst ddist ddist iddst didst disdt idsdt dsidt sdidt isddt siddt ddsit ddsit dsdit sddit dsdit sddit idsdt disdt isddt siddt dsidt sdidt didts iddts ddits ddits iddts didts ditds idtds dtids tdids itdds tidds ddtis ddtis dtdis tddis dtdis tddis idtds ditds itdds tidds dtids tdids distd idstd dsitd sditd isdtd sidtd ditsd idtsd dtisd tdisd itdsd tidsd dstid sdtid dtsid tdsid stdid tsdid istdd sitdd itsdd tisdd stidd tsidd ddsti ddsti dsdti sddti dsdti sddti ddtsi ddtsi dtdsi tddsi dtdsi tddsi dstdi sdtdi dtsdi tdsdi stddi tsddi dstdi sdtdi dtsdi tdsdi stddi tsddi idstd distd isdtd sidtd dsitd sditd idtsd ditsd itdsd tidsd dtisd tdisd istdd sitdd itsdd tisdd stidd tsidd dstid sdtid dtsid tdsid stdid tsdid
Note: these 'words' (valid or invalid) are all the permutations of the word didst. These words are obtained by scrambling the letters in didst.