ffff ffrr ffss fftf frst fssf ftrs ftsr fuff fufu fur- furr furs furt fuss fust fusu futs futu rrrr rsts rstu rtss rtts ruff ruft rurs ruru russ rust rusu ruts rutt rutu sfss sfsu sfts srtr ssrs sssf ssss ssts stfu strs stru stsf stss sttr stuf stur stus stut suf- suff sufr sufs sufu sur- surf surr surs surt suru sus- suss sust susu sutu suus tfrs tfss trfr trst trtr trus trut truu tssf tssr tsst tsts ttff ttss tttt tuff tuft tufu turf turr turs turt turu tuss tust tuts tutt tutu urff urft urss ursu urts urur urus urut usfs ussf ussr usss usst ussu usts usus uttu uutf uuuu