-er b-u bbb bbe bbo bbr bbt bbu be- beb bee beo ber bet beu bob boe boo bor bot bou brb bre bro brr brt bru btb bte bto btr btt btu bub bue buo bur but buu ebb ebe ebo ebr ebt ebu eeb eee eeo eer eet eo- eob eoe eoo eor eot eou erb ere ero err ert eru etb ete eto etr ett etu eu- eub eue eur eut ob- obb obe obo obr obt obu oeb oee oeo oer oet oo- oob ooo oor oot or- orb ore oro orr ort oru ot- otb ote oto otr ott otu ou- oue ouo our out rbb rbe rbo rbr rbt rbu re- reb ree reo rer ret reu rob roe roo ror rot rou rrb rrr rrt rru rtb rte rto rtr rtt rtu rub rue ruo rur rut ruu tbb tbe tbo tbr tbt tbu te- teb tee teo ter tet teu to- tob toe too tor tot tou trb tre tro trr trt tru ttb tte tto ttr ttt ttu tub tue tuo tur tut tuu ubb ube ubo ubr ubt ubu ueb uee uer uet uob uoe uoo uor uot ur- urb ure uro urr urt uru utb ute uto utr utt utu uue uur uut uuu

bbbb bbeb bbet bebb bebe bebo beeb beer beet beo- beor beot bere bero berr bert beru bete beto bett betu beur bobb bobe bobo bobu boee boeo boer boet boob booe boor boot bor- bore boro borr bort boru botb bote boto bott boue bour bout breb bree breo brer bret brob broe broo bror brot brou brrr brue brut btob btor btrt bttb bubb bube bubo bubu buer bueu bur- burb bure buro burr burt buru but- bute buto butt ebbo ebbr eber eboe eboo ebor ebro ebru ebur eeee eero eete eetu eore eoto erbb erbe ereb erer eret erob eroe eroo erre erro ertu erub erur etbr etee eter etoe etre etro ette etto ettu euer eur- eure euro eurt o-eo obbo ober obet oboe obor obot obre obro oere oobe ooer oooo oore oort ootb orbb orbe orbo orbu ore- oreb oreo orer oro- oroe oror orot orro orte orto orub otee oter oto- otoe otoo otor otre otro otte otto ottu otur ouer our- oure ouro ourt out- outb oute outo ouu- rbbb rbbr rebb rebe rebo rebu reeb reet reot reou rere rero rert reru rete reto retr rett reue reut reuu rob- robb robe robo robt robu roer roet roob roor root rore roro rort roru rote roto rotr rott roub roue rout rrrr rtee rubb rube rubu ruer ruet rure ruro ruru rute ruto rutt rutu tbrb tebo tebu teer teet teor ter- tere tero terr teru tete teto tetr tett tetu teut tobe tobo tobt tobu toee toer toet toor toot tore toro torr tort toru tote toto totr tott tour tout tre- tree treo tret treu troe troo trot trou trte trtr trub true trut truu ttbb tteo tter ttoe tttt tubb tube tubo tubr tubu tuer tuet tuor turb ture turo turr turt turu tute tuto tutt tutu tuuo ubbe ubbo uber ubet uor- uore urbe ure- uret uro- uroo urre urte urur urut uter utor utto uttu uuuu

-tree bbbee be-er be-ro beber bebot beebe beete beeut beote beour berbe beret berob beroe beror berre berru berte berto betee beter betoo betor betou betre bett- bette betto beuer beure beute bo-bo bobet bobr bobre boero boeur booer boore boort booru borbo boree borer boret boro- boroo borot borou borre borro borut botet botou botro botte bottu bouee bouer bouet boure boute bouto brebu breer breet breo- brere breto brett breu- brobo broer broto broue brout brrrr bruer bruet brute btr-t bubbe buber buret buroo burro burru burte burtt burut buteo buter buto- butor butot butou butte butuo butut ebber ebbet ebert eboue ebure eeeee eorre erbbe erber erere eroor erore eroto error errtu erte erter etete etoro etour etree etter eturu eubro euro- eurre o-r-b obbet obert obete oboro obote oboue obout obreb oo-er ooooo orbot oreo- orere orero orobe orobo oroer orout orret orter ortet ortoo orube oruro orutu otere otero ototo otour otter ottur oture oubut ouert ouoro oure- outer outre outro outto rebbe reber rebet rebut reere rere- reree reret rerob retee reter retro rette retto reuer reuet reute ro-ro robbe robbo rober robo- robor robot robrt robte robur roero rooer roore roote rooue rorbu rorer roteb roter roto- rotor rotot rotte rotto roubt rouer rouet roure route routt rubee ruber rubor ruere ruete ruter rutte ruutu tbtbt tbutt teber tebet teret tereu teror terre terro tert- teruo teter tetr- tetro tette teuto to-be tobbe tober tobet tobor tobot tobou tobre toerr toeto toobe toore torbe toreo toret torob torre torro torte torto tortu torue toter toto- totoe totoo totte toure touro toute treer treet trere trete trett treut troee trott troue trout trubu truer truro trute ttttt tuber tubo- tubou tuero tuotu turbe turbo turbt turet turot turre turro turtu turut tutee tuteo tutor tutte tutto tuuru uber- ubobo uouee ureo- uroob urour urter urubu urutu utebo uter- utero utro- utror utter uttur utube uturu ututo uuuuu

b-tree bbbbbb bebeto bebout beebee beeter berbee berbeo berber bereet berere berour berrer berret bertre berube betere betete betrue bettee better bettor betutu beurre bobber bobete bobote boeber boerre boober booboo bootee booter booue borbor boreto borore bororo borte botere botero botete botoro botree botter boture boubou boueer bouree bourou bourre bouter boutet boutob boutre boutte breere brette bretuo breuer broter brotto brouet broute brubru bruree brutto bubber bububu burbet burbot burbur burotu burree burrer burret burutu butbro butere butter buttto buutuo ebbert ebbout eburru eebree eototo erbree eroto- errett errour etoeot ettore ettutu euroto eururo eutere euttob oberto obrute obtree obturb oerter oooooo orrour ottoor ouerre out-be outour outreb outter outtro r-tree reboot rebore rebote rebour rebute rerobe reroot reteer reteet reteoo retere retore retort retour retree retret retro- retrot