wdif dwif widf iwdf diwf idwf wdfi dwfi wfdi fwdi dfwi fdwi wifd iwfd wfid fwid ifwd fiwd difw idfw dfiw fdiw ifdw fidw
Note: these 'words' (valid or invalid) are all the permutations of the word wdif. These words are obtained by scrambling the letters in wdif.