bbbb bbbs bnss bsns bsts btss bttb btus bubb bubs bubu bunb bunn buns bunt bunu buss bust busu but- buts butt buus nnnn nnss nntn nssb nsss nsts nstu nsub ntnu ntsb ntss ntsu nubs nunn nuns nunt nuss nust nusu nuts nutt nutu sbbs sbst sbtn sbus snns snub snus ssbn ssns sssb ssss sstb ssts stbs stnn stns stss stub stun stus stut sub- subb subs sun- sunb sunn suns sunt sunu sus- suss sust susu sutu suus tbbs tbst tnts tnut tsst tsts tsun ttbb ttss tttt tubb tubs tubu tunb tunn tuns tunu tuss tust tuts tutt tutu unns uns- unst untb unts unus unut usbs usnu ussb usss usst ussu ustb usts usun usus uttu uuuu