imbf mibf ibmf bimf mbif bmif imfb mifb ifmb fimb mfib fmib ibfm bifm ifbm fibm bfim fbim mbfi bmfi mfbi fmbi bfmi fbmi
Note: these 'words' (valid or invalid) are all the permutations of the word imbf. These words are obtained by scrambling the letters in imbf.