nkfl knfl nfkl fnkl kfnl fknl nklf knlf nlkf lnkf klnf lknf nflk fnlk nlfk lnfk flnk lfnk kfln fkln klfn lkfn flkn lfkn
Note: these 'words' (valid or invalid) are all the permutations of the word nkfl. These words are obtained by scrambling the letters in nkfl.