knub nkub kunb uknb nukb unkb knbu nkbu kbnu bknu nbku bnku kubn ukbn kbun bkun ubkn bukn nubk unbk nbuk bnuk ubnk bunk
Note: these 'words' (valid or invalid) are all the permutations of the word knub. These words are obtained by scrambling the letters in knub.