fmcu mfcu fcmu cfmu mcfu cmfu fmuc mfuc fumc ufmc mufc umfc fcum cfum fucm ufcm cufm ucfm mcuf cmuf mucf umcf cumf ucmf
Note: these 'words' (valid or invalid) are all the permutations of the word fmcu. These words are obtained by scrambling the letters in fmcu.