-er b-u bbb bbe bbk bbo bbr bbt bbu be- beb bee bek beo ber bet beu bkb bke bkk bko bkr bkt bob boe bok boo bor bot bou brb bre brk bro brr brt bru btb bte btk bto btr btt btu bub bue buk buo bur but buu ebb ebe ebk ebo ebr ebt ebu eeb eee eek eeo eer eet ekb eke eko ekr ekt eku eo- eob eoe eok eoo eor eot eou erb ere erk ero err ert eru etb ete etk eto etr ett etu eu- eub eue eur eut k-t kbb kbe kbk kbo kbr kbu ke- keb kee kek keo ker ket kkb kke kkk kkr kkt kku kob koe kok koo kor kot kou krk kro krr krt kru ktb kte ktk kto ktr ktt ktu kub kue kuk kur kut kuu ob- obb obe obk obo obr obt obu oeb oee oeo oer oet okb oke okk oko okr oku oo- oob ook ooo oor oot or- orb ore ork oro orr ort oru ot- otb ote otk oto otr ott otu ou- oue ouk ouo our out rbb rbe rbk rbo rbr rbt rbu re- reb ree rek reo rer ret reu rkb rke rkk rko rkt rku rob roe rok roo ror rot rou rrb rrk rrr rrt rru rtb rte rtk rto rtr rtt rtu rub rue ruk ruo rur rut ruu tbb tbe tbk tbo tbr tbt tbu te- teb tee tek teo ter tet teu tkb tke tkk tko tkr tkt to- tob toe tok too tor tot tou trb tre trk tro trr trt tru ttb tte ttk tto ttr ttt ttu tub tue tuk tuo tur tut tuu ubb ube ubk ubo ubr ubt ubu ueb uee uer uet ukb uke ukk ukr uku uob uoe uok uoo uor uot ur- urb ure urk uro urr urt uru utb ute utk uto utr utt utu uue uur uut uuu

bbbb bbeb bbet bebb bebe bebo beeb beek beer beet beke beko beo- beok beor beot bere berk bero berr bert beru bete beto bett betu beuk beur bobb bobe bobo bobu boee boeo boer boet boke boko boku boob booe book boor boot bor- bore bork boro borr bort boru botb bote boto bott boue bouk bour bout breb bree brek breo brer bret brkb brob broe brok broo bror brot brou brrr brue brut btek btob btor btrt bttb bubb bube bubo bubu buer bueu buke bukk buko buku bur- burb bure burk buro burr burt buru but- bute buto butt ebbo ebbr eber eboe eboo ebor ebro ebru ebur eeee eeke eero eete eetu ekeb ekek eker eket ekur eore eoto erbb erbe ereb erer eret erke erob eroe eroo erre erro ertu erub erur etbr etee eter etoe etok etre etro ette etto ettu euer eur- eure euro eurt kbbb kbbe kbbk kbbo kbbr kbbt kbbu kbeb kbee kbek kbeo kber kbet kbkb kbkk kbko kbkr kbob kboe kbok kboo kbot kbrb kbre kbrk kbro kbrt kbru kbtb kbte kbtk kbto kbtr kbtt kbub kbue kbuk kbur kbut kbuu kebb kebe kebr kebt kebu keek keer keet kekb keke keko keku keok ker- kerb kere kerk kero kerr kert keru ket- kete ketk keto ketr kett ketu keur kkbb kkbe kkbo kkbr kkbt kkkk kkob kkoo kkor kkot kkrb kkre kkrk kkro kkrr kkrt kktk kktu kkut kkuu kobb kobe kobk kobo kobr kobu kokb koke kokk koko kokr koku koob kook kooo koor koot koou korb kore kork koro korr kort koru kotb kote kotk koto kotr kott kotu koub koue kour kout kouu krbb krbe krbk krbr krbt kreb kree krek kreo kret kreu krke krkk krko krkr krku krob kroe krok kroo kror krrb krre krrk krro krrr krrt krtk krto krtr krue kruk krur ktbb ktbr ktbt ktbu ktee ktek ktkb ktke ktkk ktko ktkr ktkt ktku ktob ktoe ktok ktoo ktor ktot ktrb ktre ktrk ktro ktrr ktrt ktru kttk ktto kttr kttt kttu ktub kubb kube kubo kubr kubu kuek kueu kuke kukk kuku kuok kuoo kurb kure kurk kuro kurr kurt kuru kute kuto kutr kutt kutu kuub kuuk kuur kuuu o-eo obbo ober obet obkb oboe obok obor obot obre obro oere oker oket okko okok okor okot okre okro okto okur oobe ooer ooku oooo oore oort ootb orbb orbe orbo orbu ore- oreb orek oreo orer orke orko oro- oroe orok oror orot orro orte orto orub otee oter oto- otoe otok otoo otor otre otro otte otto ottu otur ouer our- oure ouro ourt out- outb oute outo ouu- rbbb rbbr rebb rebe rebk rebo rebu reeb reek reet reke reko rekt reot reou rere rero rert reru rete reto retr rett reue reuk reut reuu rob- robb robe robo robt robu roer roet roke rokk roko rokr roku roob rook roor root rore rork roro rort roru rote rotk roto rotr rott roub roue rouk rout rrrr rtee rubb rube rubu ruer ruet ruke rukk ruku ruok rure ruro ruru rute ruto rutt rutu tbrb tebo tebu teek teer teet teke teok teor ter- tere terk tero terr teru tete teto tetr tett tetu teuk teut tobe tobo tobt tobu toee toek toer toet toke toko toku took toor toot tore tork toro torr tort toru tote toto totr tott touk tour tout tre- tree trek treo tret treu troe troo trot trou trte trtr trub true truk trut truu ttbb tteo tter ttoe tttt tubb tube tubo tubr tubu tuer tuet tuke tuko tuor turb ture turk turo turr turt turu tute tuto tutt tutu tuuo ubbe ubbo ubek uber ubet ukek ukeu ukko ukok ukur uoke uor- uore urbe ure- uret urke uro- urok uroo urre urte uruk urur urut uter utor utto uttu uuuu

-tree b-r-k bbbee bbook be-er be-ro bebek beber bebot beebe beeke beete beeut beker bekke bekko bekok beote beour berbe berek beret berk- berke berko berob beroe berok beror berre