bbbb bbbs bbpr bibb bibi bibs biis bipp bips birb biri birr birs birt bis- bisp biss bist bits bitt bpti bris brit brrr brrs brsb brsr brst bspp bspr bsts btbp btps btrt btss bttb ibis ibri ibss ibtb ibts iiii iiis iiit iirs iisi iisp iisr iist iitr iitt ippr ipri ipsi ipsp ipss ipts irbp iri- irip iris irps irri irrs irsp irti irtp irts isbt isis isit ispr isps isri isrp issi issp issr isss isti istp istr ists itbs itis itri itrs itsi itsp pbrs pbsp pibb pibi piip pipi pipp pips piri pirr pirs pisi piss pist piti pitr pits pitt ppib pppp ppps ppss ppts pptt prbs pri- prii pris prps prri prrs prsi prss prti prtp prtr psbr psbt psip psis pspi pspp pspr psps psrp psst psts rbbb rbbr rbbs rbis rbsp rbss rbst rib- ribs riis ripi ripp ripr rips ript riri rirs risi risp riss rist riti rits ritt rpii rpps rpts rrrr rrsp rsbi rsis rspb rsps rstp rsts rtps rtss rttp rtts s-ib s-ii sbbs sbsi sbsp sbst sibi sibs siit sipi sipp sips sipt siri sirp sirr sirs sirt sisi siss sist sit- siti sits sitt spib spip spir spis spit spps spri sprs spsp spss spst sptb sptr spts srib sris srps srpt srsp srtp srtr ssbr ssis ssit ssps sspt ssri ssrs sssb sssi ssss sstb sstp ssts stbs stib stip stir stis stit stpp stps stri strs stsi stss sttr tbbs tbit tbrb tbsp tbst tbtp tibi tibs tiit tip- tipi tipp tips tipt tirb tiri tirr tirs tisb tisi tiss tist titi titp tits titt tpir tppp tppr tprs tptp tptr tri- trib trip tris trit trpp trps trsi trst trtr tsis tsps tspt tssi tssr tsst tsts ttbb ttss tttt