fnnb nfnb fnnb nfnb nnfb nnfb fnbn nfbn fbnn bfnn nbfn bnfn fnbn nfbn fbnn bfnn nbfn bnfn nnbf nnbf nbnf bnnf nbnf bnnf
Note: these 'words' (valid or invalid) are all the permutations of the word fnnb. These words are obtained by scrambling the letters in fnnb.