fbhi bfhi fhbi hfbi bhfi hbfi fbih bfih fibh ifbh bifh ibfh fhib hfib fihb ifhb hifb ihfb bhif hbif bihf ibhf hibf ihbf
Note: these 'words' (valid or invalid) are all the permutations of the word fbhi. These words are obtained by scrambling the letters in fbhi.