-ous bbbb bbbs bffs bfsr bfts bftt bobb bobo bobs bobu boff bofs bofu boob boof boor boos boot bor- borf boro borr bors bort boru boso boss bost bosu botb boto bots bott bouf bour bous bout brfu brob broo bror bros brot brou brrr brrs brsb brsr brst brus brut bsff bsfs bsos bsts btob btor btrt btss bttb btus bubb bubo bubs bubu buff bufo bufr bur- burb buro burr burs burt buru buss bust busu but- buto buts butt buus fbrs fbus ffff ffrr ffss fftf fobs fobt fofo foof foos foot for- forb foro forr fors fort fosb foso foss fost foto fots fott four fous fout frob fros frot frou frsb frso frst frub fsfo fssf ftos ftrs ftsr ftub fubb fubs fubu fuff fufu fuor fur- furo furr furs furt fuso fuss fust fusu futo futs futu obbo obor obos obot obro obsr obss obst obts obus off- offo offr offs offu ofor ofst ofus ooff oofs oooo ooos oort oost ootb oots oous orbb orbo orbs orbu orff orfs orfu oro- orof oror oros orot orro orrs orso orsu orto orts orub orus osoo osor osos osro ossb osso ossu ostr osts otbs oto- otof otoo otor otos otro otrs otso otsu otto otts ottu otur otus oubs ouff our- ouro ours ourt oust out- outb outo outs ouu- rbbb rbbr rbbs rbss rbst rob- robb robo robs robt robu roff rofo roob roof roor roos root roro rort roru roso ross rost roto rotr rots rott roub rouf rous rout rrrr rsos rsts rstu rtbf rtfb rtss rtts rubb rubs rubu ruff rufo ruft ruro rurs ruru ruso russ rust rusu ruto ruts rutt rutu s-os sbbs sbor sbot sbst sbus sfor sfos sfro sfss sfsu sfts sobo sobr sobs sobt sobu sofo soft soof soor soos soot sorb soro sorr sors sort soru soso soss sost soto sots sotu souf sour sous sout sros srtr srub ssbr ssot ssrs sssb sssf ssss sstb ssts stbs stfu stob stof stoo stor stos stot stou stro strs stru stsf stss sttr stub stuf stur stus stut sub- subb subo subs suf- suff sufr sufs sufu suor suos sur- surf suro surr surs surt suru sus- suso suss sust susu suto sutu suus tbbs tbrb tbst tfot tfrs tfss tobo tobs tobt tobu toff tofo toft tofu toof toor toos toot torf toro torr tors tort toru tosb toso toss tost tosu toto totr tots tott tour tous tout trfr troo tros trot trou trst trtr trub trus trut truu tsob tsos tsou tssf tssr tsst tsts ttbb ttff ttss tttt tubb tubo tubr tubs tubu tuff tufo tuft tufu tuor tuos turb turf turo turr turs turt turu tuss tust tuto tuts tutt tutu tuuo ubbo ubos ubtf ufos uofo uor- urbs urff urft uro- uroo urso urss ursu urts urur urus urut usbr usbs usfs usos ussb ussf ussr usss usst ussu ustb usto usts usus utfo utor utto uttu uutf uuuu