-er bbb bbe bbf bbo bbr bbt be- beb bee bef beo ber bet bfb bfe bff bfo bfr bft bob boe bof boo bor bot brb bre brf bro brr brt btb bte btf bto btr btt ebb ebe ebf ebo ebr ebt eeb eee eef eeo eer eet ef- efb efe eff efo efr eft eo- eob eoe eof eoo eor eot erb ere erf ero err ert etb ete etf eto etr ett fbb fbe fbf fbo fbr fbt feb fee fef feo fer fet ffe fff ffo ffr fft fob foe fof foo for fot frb fre frf fro frr frt ftb fte ftf fto ftr ftt ob- obb obe obf obo obr obt oeb oee oef oeo oer oet of- ofb ofe off ofo ofr oft oo- oob oof ooo oor oot or- orb ore orf oro orr ort ot- otb ote otf oto otr ott rbb rbe rbf rbo rbr rbt re- reb ree ref reo rer ret rfb rfe rff rfo rfr rft rob roe rof roo ror rot rrb rrf rrr rrt rtb rte rtf rto rtr rtt tbb tbe tbf tbo tbr tbt te- teb tee tef teo ter tet tfb tfe tff tfo tfr tft to- tob toe tof too tor tot trb tre trf tro trr trt ttb tte ttf tto ttr ttt

bbbb bbeb bbet bebb bebe bebo beeb beef beer beet befe beff befo beft beo- beof beor beot bere bero berr bert bete beto bett bftt bobb bobe bobo boee boef boeo boer boet bofe boff boob booe boof boor boot bor- bore borf boro borr bort botb bote boto bott breb bree bref breo brer bret brob broe broo bror brot brrr btob btor btrt bttb ebbo ebbr eber eboe eboo ebor ebro eeee eefe eero eete efbr efeo efet efor eft- eore eoto erbb erbe ereb erer eret erft erob eroe eroo erre erro etbr etee eter etfb etfe etoe etre etro ette etto febo feeb feer feet fefe feff fefo feof ferb fere fero ferr fert fete fetr fett ffee ffff ffrr fftf fobt foer fofo foof foot for- forb fore foro forr fort fote foto fott free freo fret frob froe frot fter o-eo obbo ober obet oboe obor obot obre obro oere ofer off- offe offo offr ofor ofre oobe ooer ooff oooo oore oort ootb orbb orbe orbo ore- oreb oreo orer orfe orff oro- oroe orof oror orot orro orte orto otee oter oto- otoe otof otoo otor otre otro otte otto rbbb rbbr rebb rebe rebo reeb reef reet refe reff refr reft reof reot rere rero rert rete reto retr rett rfef rob- robb robe robo robt roer roet rofe roff rofo roob roof roor root rore roro rort rote roto rotr rott rrrr rtbf rtee rtfb tbrb tebo teef teer teet teff teft teor ter- tere terf tero terr tete teto tetr tett tfeb tfot tobe tobo tobt toee toer toet toff tofo toft toof toor toot tore torf toro torr tort tote toto totr tott tre- tree tref treo tret trfr troe troo trot trte trtr ttbb tteo tter ttff ttoe tttt

-tree bbbee be-er be-ro beber bebot beebe beeft beete beffe befoe befor beofe beoff beote berbe beret berob beroe beror berre berte berto betee beter betoo betor betre bett- bette betto bo-bo bobet bobr bobre boero bofet boffo booer boore boort borbo boree borer boret boro- boroo borot borre borro botet botro botte breef breer breet breo- brere breto brett brobo broer broft broto brrrr btr-t ebber ebbet ebert eeeee efere efetf effer effet efore efter eofor eorre erbbe erber erere eroor erore eroto error erte erter etete etoro etree etter febre feeor feere fefor feoff feret ferr- ferre ferro ferte feter feto- fetor fette foore foote fore- foreo foret forro forte forto fotte freer freet frere frett frobe froot frore frote ftrtt o-fer o-r-b obbet obert obete oboro obote obreb offer offof offre offto ofoto ofter oo-er ooooo orbot oreo- orere orero orfeo orfoe orfor orobe orobo oroer orret orter ortet ortoo otere otero ototo otter rebbe reber rebet reefe reeft reere refer refet reffe reffo rere- reree reret rerob retee reter retro rette retto ro-ro robbe robbo rober robo- robor robot robrt robte roero roffe rofor rooer roofe rooft roore roote rorer roteb roter roto- rotor rotot rotte rotto tbtbt teber tebet tefe teret teror terre terro tert- teter tetr- tetro tette to-be tobbe tober tobet tobor tobot tobre toeof toerr toeto tofet toffo tofor tofte toobe toore torbe toreo toret torob torre torro torte torto toter toto- totoe totoo totte treer treet trefe treff trere trete trett troee trofe troff troft trott ttttt

b-tree bbbbbb bebeto beebee beefer beeter before befree befret berbee berbeo berber bereet bereft berere berrer berret bertre betere betete bettee better bettor bobber bobete bobote boeber boerre bofete boffet boober booboo bootee booter borbor boreto borfee borore bororo borte botere botero botete botoro botree botter breefe breere breffo brette broter brotto ebbert eebree effere effete effoff effore effort efreet efter- eototo erbree eroto- errett etoeot ettore feeror feetof feofor ferber ferfer ferrer ferret ferro- fertee ferter fetter foboff foerre foeto- foetor foofoo footer forrer forrot fortee forter frbroo freebo freeof freeto frefre frette frobot froofe fterer fterre o-bofe oberto obtree oerter oferre offeet oftfor oofotr oooooo ottoor r-tree reboot rebore rebote reefer reeffe refeet refeff refert refete refoot refret refter rerobe reroof reroot reteer reteet reteoo retere retore retort retree retret retro- retrot retter robber robert roboto roofer rooter rootof rootte rorter rotter t-tree teebee teeoff teetee teeter terete terreo terrer terret terror terrot terter tertre tetete tetter to-fro tobeor toboot toetoe toffee tofore toofer tooter tootoo torero torfer tororo torret tortor totebo totoro totrot totter trebor treeof treete trefet trefor trefot trefte tretee trette troffe trotro trotte

bbbbbbb be-free beetree berbere berefet berrett bertero bertree bo-tree bobotee boe-bot boo-boo borbore boretto borrero bottero eeeroer errorof feoffee feoffer feoffor ferebee feretto ferrere ferrero foo-foo footrot forbore