-er b-u bbb bbe bbr bbs bbt bbu be- beb bee ber bes bet beu brb bre brr brs brt bru bsb bse bsr bss bst bsu btb bte btr bts btt btu bub bue bur bus but buu ebb ebe ebr ebs ebt ebu eeb eee eer ees eet erb ere err ers ert eru es- esb ese esr ess est esu etb ete etr ets ett etu eu- eub eue eur eus eut rbb rbe rbr rbs rbt rbu re- reb ree rer res ret reu rrb rrr rrs rrt rru rsb rse rsr rss rst rsu rtb rte rtr rts rtt rtu rub rue rur rus rut ruu sbb sbe sbr sbs sbt sbu se- seb see ser ses set seu sr- srb sre srr srs srt ss- ssb sse ssr sss sst ssu stb ste str sts stt stu sub sue sur sus sut suu tbb tbe tbr tbs tbt tbu te- teb tee ter tes tet teu trb tre trr trs trt tru tsb tse tsr tss tst tsu ttb tte ttr tts ttt ttu tub tue tur tus tut tuu ubb ube ubr ubs ubt ubu ueb uee uer ues uet ur- urb ure urr urs urt uru usb use usr uss ust usu utb ute utr uts utt utu uue uur uus uut uuu

bbbb bbbs bbeb bbet bebb bebe beeb beer bees beet bere berr bers bert beru bes- bese bess best bete bets bett betu beur breb bree brer bres bret brrr brrs brsb brsr brst brue brus brut bseb bsee bser bses bset bsse bsts btrt btss bttb btus bubb bube bubs bubu buer bueu bur- burb bure burr burs burt buru buse buss bust busu but- bute buts butt buus ebbr ebbs eber ebes ebru ebur ebus eeee eees eers eese eete eets eetu erbb erbe ereb erer eres eret erre errs erse erst erts ertu erub erur erus esbs esee eser eses eset esse esst essu este estr ests esus etbr etee eter etes etre etsu ette ettu euer eur- eure eurt euse rbbb rbbr rbbs rbss rbst rebb rebe rebs rebu reeb rees reet rere rers rert reru rese ress rest rete retr rets rett reue reus reut reuu rrrr rsee rsre rsts rstu rtee rtes rtss rtts rubb rube rubs rubu ruer rues ruet rure rurs ruru ruse russ rust rusu rute ruts rutt rutu sbbs sber sbse sbst sbus se-e se-s se-t se-u sebe sebs sebt seeb seer sees seet seeu serb sere serr sers sert seru sese sess sest set- sete sets sett seur sreb sres srtr srub ssbr ssee sses sset ssrs sssb ssss sstb ssts stbs stee ster stes stet stre strs stru stss sttr stub stue stur stus stut sub- subb subs suee suer sues suet sueu sur- sure surr surs surt suru sus- suse suss sust susu sute sutu suus tbbs tbrb tbst tebu teer tees teet ter- tere terr ters teru tese tess test tete tetr tets tett tetu teut tre- tree tres tret treu trst trte trtr trub true trus trut truu tses tset tsse tssr tsst tsts ttbb tter ttss tttt tubb tube tubr tubs tubu tuer tues tuet turb ture turr turs turt turu tuss tust tute tuts tutt tutu ubbe uber ubet uers uess urbe urbs ure- ures uret urre urse urss ursu urte urts urur urus urut usbe usbr usbs usee user uses uset ussb usse ussr usss usst ussu ustb uste usts usus uter utes uttu uuuu

-tree bbbee bbser bbuss be-er beber bebes beebe beebs beers beest beete beets beeut berbe beres beret berre berru berse berte berts berus besee beset besse beste bests besut betee beter betes betre betrs bett- bette betts betus beuer beure beust beute brebu breer brees breet brere brers brese bress brest brets brett breu- brrrr bruer brues bruet bruse bruss brust brute bsure btr-t btstu bubbe buber burbs bures buret burrs burru burse burst burte burts burtt burus burut buser buses busse bussu buste busts busur busut busuu buter butes butte butts butut ebber ebbet ebers ebert ebure eeeee erbbe erber erebs erere erest erets erres errtu erses erste ersts erte erter ertes erubs eruts esbus esere esser esses essse essue estee ester estes estet estre estur estus esure etest etete etree etres etter ettes eturu eurre eurus euser rebbe reber rebet rebts rebus rebut reere reese reest rere- reree reres reret resee reses reset resse reste restr rests resue resus retee reter retes retsu rette retts reuer reuet reuse reuss reute rsust rubee ruber rubes rubus ruere ruers ruete ruses russe ruste rusts rustu ruter rutte ruutu s-bus sebbe sebes sebet seebe seere seers seese seest seesu seete serbs serer seres seret serre serse serss sert- serte serts serue serut seser seses sesse seste sestu sesue setee seter setse sette setts settu setus setut seuer seure seuss seute sssrb sssss steer stees steet stere sterr sters stert stesu stete stets steur strbe streb stree stret streu strrs strub strue strut stube stubs stuer sturb sture sturt stuse stuss stute stuue subbu suber subss subst suere suers suess suest suete suets sueur surer sures surre surte surtr surur surus suser suses susse susus sutee suter sutes sutte suttu tbtbt tbutt teber tebet teebs teers teese teest teets teres teret tereu terre terrs terse tert- tesse teste tests teter tetes tetr- tetsu tette teuts treer trees treet trere tres- trese tress trest trete trets trett treus treut trubs trubu truer trues truse truss trust trute truus tsebe tsere tsets tsuru tsuur ttest ttttt ttusb tubbs tuber tubes turbe turbt turet turre turse turss turst tursu turtu turut tutee tutte tutus tuuru uber- ubers urbes ursus urter urubu urutu usees users usest usses uster ustur usure usutu uter- utter uttur utube uturu uuuuu

b-tree bbbbbb bbsers beebee beebes beerse beerst beeste beeter berbee berber berbes bereet berere berest berets berrer berres berret bersee berset bertes bertre bertus berube berust besbes besbre besert besets besser besses besset bessus bester