bbbb bbbs bbpr bibb bibi bibs biis bipp bips bipu birb biri birr birs biru bis- bisp biss bisu bpsu bris brrr brrs brsb brsr brup brus bspp bspr bsup bubb bubi bubs bubu buir buis buiu bups bur- burb buri burp burr burs buru busi buss busu buus ibis ibri ibss ibus iiii iiis iirs iisi iisp iisr iisu ippr ipri ipsi ipsp ipss ipur ipus irbp iri- irip iris irps irri irrs irsp irus isis ispr isps isri isrp issi issp issr isss issu isup isus iuiu iupp iuss pbrs pbsp pibb pibi piip pipi pipp pips piri pirr pirs piru pisi piss pisu pius ppib pppp ppps ppru ppss ppur prbs pri- prii pris prps prri prrs prsi prss prus pruu psbr psip psis pspi pspp pspr psps psrp pubs pubu puir puis puiu pupi pups pupu pur- purb puri purp purr purs puru pusi puss rbbb rbbr rbbs rbis rbsp rbss rib- ribs ribu riis ripi ripp ripr rips riri rirs risi risp riss risu rius rpii rpps rrrr rrsp rsbi rsis rspb rsps rubb rubi rubp rubs rubu ruis rupp ruri rurp rurs ruru rusi russ rusu s-ib s-ii sbbs sbsi sbsp sbus sibi sibs sibu sipi sipp sips siri sirp sirr sirs siru sisi siss sisu siui sius spib spip spir spis spps spri sprs spsp spss spui spur spus srib sris srps srsp srub ssbr ssis ssps ssri ssrs sssb sssi ssss sub- subb subi subs suir suis sup- supp supr sups sur- suri surp surr surs suru sus- susi susp suss susu suus u-rp ubbi ubii ubir ubis uipi uirr upis uppp uppu upri upsi upup urbi urbs urib uris uriu urri ursi urss ursu urup urur urus usbr usbs usip usis uspp usps ussb ussr usss ussu usui usus uuri uusi uuuu