-er bbb bbe bbk bbr bbs bbt be- beb bee bek ber bes bet bkb bke bkk bkr bks bkt brb bre brk brr brs brt bsb bse bsk bsr bss bst btb bte btk btr bts btt ebb ebe ebk ebr ebs ebt eeb eee eek eer ees eet ekb eke ekr eks ekt erb ere erk err ers ert es- esb ese esk esr ess est etb ete etk etr ets ett k-t kbb kbe kbk kbr kbs ke- keb kee kek ker kes ket kkb kke kkk kkr kks kkt krk krr krs krt ksb kse ksk ksr kss kst ktb kte ktk ktr kts ktt rbb rbe rbk rbr rbs rbt re- reb ree rek rer res ret rkb rke rkk rks rkt rrb rrk rrr rrs rrt rsb rse rsk rsr rss rst rtb rte rtk rtr rts rtt sbb sbe sbk sbr sbs sbt se- seb see sek ser ses set sk- skb ske skk skr sks skt sr- srb sre srk srr srs srt ss- ssb sse ssk ssr sss sst stb ste stk str sts stt tbb tbe tbk tbr tbs tbt te- teb tee tek ter tes tet tkb tke tkk tkr tks tkt trb tre trk trr trs trt tsb tse tsk tsr tss tst ttb tte ttk ttr tts ttt

bbbb bbbs bbeb bbet bebb bebe beeb beek beer bees beet beke beks bere berk berr bers bert bes- bese besk bess best bete bets bett breb bree brek brer bres bret brkb brrr brrs brsb brsr brst bseb bsee bser bses bset bskt bsse bsts btek btrt btss bttb ebbr ebbs eber ebes eeee eees eeke eeks eers eese eesk eete eets ekeb ekek eker ekes eket erbb erbe ereb erer eres eret erke erks erre errs erse erst erts esbs esee esek eser eses eset eske esks esse esst este estr ests etbr etee eter etes etre ette kbbb kbbe kbbk kbbr kbbs kbbt kbeb kbee kbek kber kbes kbet kbkb kbkk kbkr kbrb kbre kbrk kbrt kbsb kbsk kbsr kbss kbst kbtb kbte kbtk kbtr kbts kbtt kebb kebe kebr kebt keek keer kees keet kekb keke keks ker- kerb kere kerk kerr kers kert kesb kesk kesr kess kest ket- kete ketk ketr kets kett kkbb kkbe kkbr kkbs kkbt kkkk kkrb kkre kkrk kkrr kkrs kkrt kkse kksr kkss kkst kktk kkts krbb krbe krbk krbr krbt kreb kree krek kres kret krke krkk krkr krks krrb krre krrk krrr krrs krrt krse krsk krsr krss krst krtk krtr krts ksbr ksbs ksee ksek kser kset kskb kske kskk kskr ksks ksrb ksrr ksrs ksrt ksse kssr ksss ksst kstb kste kstk kstr ksts kstt ktbb ktbr ktbt ktee ktek ktkb ktke ktkk ktkr ktks ktkt ktrb ktre ktrk ktrr ktrs ktrt ktsr ktst kttk kttr ktts kttt rbbb rbbr rbbs rbss rbst rebb rebe rebk rebs reeb reek rees reet reke reks rekt rere rers rert rese ress rest rete retr rets rett rkss rkts rrrr rsee rsre rsts rtee rtes rtss rtts sbbs sber sbrk sbse sbst sbtk se-e se-k se-s se-t sebe sebs sebt seeb seek seer sees seet seke sekk sekt serb sere serk serr sers sert sese sess sest set- sete sets sett skee sker skes sket skrt skss sreb sres srtr ssbr ssee sses sset ssrs sssb ssss sstb ssts stbs stee stek ster stes stet stks stre strk strs stss sttr tbbs tbrb tbst teek teer tees teet teke ter- tere terk terr ters tese tess test tete tetr tets tett tkts tre- tree trek tres tret trst trte trtr tses tset tsks tsse tssr tsst tsts ttbb tter ttss tttt

-tree b-r-k bbbee bbser be-er bebek beber bebes beebe beebs beeke beers beest beete beets beker bekes bekke berbe berek beres beret berk- berke berks berre berse berte berts besee beset besse beste bests betee beter betes betke betre betrs bett- bette betts breek breer brees breet breke brere brers brese bress brest brets brett brrrr bskts btr-t ebber ebbet ebers ebert eeeee ekers ekker erbbe erber erebs erere eresk erest erets erres erses erste ersts erte erter ertes esere esker esser esses essse estee ester estes estet estre eteke etest etete etree etrek etres etter ettes k-set k-t-b kebbe kebek keber keeks keere keest keets kerbs kerek keres keret kerre kerrs kerse kerss keser kesse keste ketek keter kette krebs kreek krees kreke kresk kress krest krete rebbe reber rebet rebts reeks reere reese reesk reest rekke rere- reree reres reret resee reses reset reske resse reste restr rests retee reter retes rette retts rt-rk sebbe sebek sebes sebet seebe seeke seeks seere seers seese seest seete seker sekes sekke serbs serer seres seret serke serre serse serss sert- serte serts seser seses sesse seste setee seter setse sette setts skeer skees skeet skere skers skete skrte sssrb sssss steek steer stees steet steke stere sterk sterr sters stert stete stets stker strbe streb stree strek stret strrs tbtbt teber tebet teebs teers teese teest teets tekes teket tekke terek teres teret terre terrs terse tersk tert- tesse teste tests teter tetes tetr- tette treer trees treet treks trere tres- trese tress trest trete trets trett trsek tsebe tsere tsets ttest ttttt

b-tree bbbbbb bbsers beebee beebes beeker beekes beerse beerst beeste beeter bekker berbee berber berbes bereet bereke berere berest berets berker berkes berrer berres berret bersee berset bertes bertre besbes besbre beseek beseke beserk besert besets besser besses besset bester betere betete bettee better bettes brebes breeks breere breese breest brekke breres bresse breste brests brette bretts bs-tbs ebbers ebbert ebbest ebbets eberts eebree erbree eretes errest errett erster esbeek eskers eskert eskett essebt essert essess esssse estees esters estree estres estter esttes k-tree kebber keeker kekes kerber kereks kerker kersee kerser kertee kesses kester ketter kreese kreker kresek kresse kreste kretek r-tree rebbes rebesk rebets reeker reekes reeser reeses reests rerees reseek resees resets resket rester restes restte reteer retees reteet retere