bbbb bbbs bbpr bnpp bnrr bnss bpsu brns brrr brrs brsb brsr brun brup brus bsns bspp bspr bsup bubb bubs bubu bunb bunn buns bunu bups bur- burb burn burp burr burs buru buss busu buus n-up nbpp nbps nbsp nnnn nnpr nnss npss nrpn nrps nrsp nsnr nsps nssb nssp nssr nsss nsub nubs nunn nuns nups nurn nurp nurr nurs nuru nuss nusu pbrs pbsp pnpp pnup pppn pppp ppps ppru ppss ppur prbs prnp prps prrs prss prus pruu psbr psnr pspp pspr psps psrp pubs pubu puns punu pups pupu pur- purb purp purr purs puru puss rbbb rbbr rbbs rbsp rbss rnbr rnsp rppn rpps rrrr rrsp rrun rsnn rsnr rspb rsps rubb rubp rubs rubu runn runs rupp rurp rurs ruru russ rusu ruun sbbs sbsp sbus snns snpp snrs snub snur snus spns spps sprs spsp spss spun spur spus srnn srps srsp srub ssbn ssbr ssns ssps ssrs sssb ssss sub- subb subs sun- sunb sunn suns sunu sup- supp supr sups sur- surn surp surr surs suru sus- susp suss susu suus u-rp unns unps unrs uns- unus upnp uppp uppu upup urbs urns urss ursu urun urup urur urus usbr usbs usnr usnu uspp usps ussb ussr usss ussu usun usus uuuu