xfac fxac xafc axfc faxc afxc xfca fxca xcfa cxfa fcxa cfxa xacf axcf xcaf cxaf acxf caxf facx afcx fcax cfax acfx cafx
Note: these 'words' (valid or invalid) are all the permutations of the word xfac. These words are obtained by scrambling the letters in xfac.