a-a a-b a-c aaa aab aac aak aan aao aar aau ab- aba abb abc abk abn abo abr abu ac- aca acb acc ack acn aco acr acu aka akb akc akk akn ako akr aku an- ana anb anc ank ann ano anr anu aoa aob aoc aok aon aoo aor aou ar- ara arb arc ark arn aro arr aru au- aua aub auc auk aun auo aur b-u baa bab bac bak ban bao bar bau bba bbb bbc bbk bbn bbo bbr bbu bca bcb bcc bck bcn bco bcr bcu bka bkb bkc bkk bkn bko bkr bna bnb bnc bnk bnn bno bnr bnu boa bob boc bok bon boo bor bou bra brb brk brn bro brr bru bua bub buc buk bun buo bur buu c-- caa cab cac cak can cao car cau cba cbb cbc cbk cbn cbo cbr cbu cca ccb ccc cck ccn cco ccr ccu cka ckb ckc cko cn- cna cnb cnc cnn cno cnr cnu co- coa cob coc cok con coo cor cou cra crb crc crk crn cro crr cru cua cub cuc cuk cun cuo cur cuu ka- kaa kab kac kak kan kao kar kau kba kbb kbc kbk kbn kbo kbr kbu kca kcb kcc kck kcn kcr kcu kkb kkc kkk kkn kkr kku kn- kna knc knk knn kno knr knu koa kob koc kok kon koo kor kou kra krc krk krn kro krr kru kub kuc kuk kun kur kuu naa nab nac nak nan nao nar nau nba nbb nbc nbk nbn nbo nbr nbu nca ncb ncc nck ncn nco ncr ncu nka nkc nkk nkn nko nkr nku nna nnb nnc nnk nnn nno nnu no- noa nob noc nok non noo nor nou nra nrb nrc nrk nrn nro nrr nru nua nub nuc nuk nun nuo nur nuu oaa oab oac oak oan oao oar oau ob- oba obb obc obk obn obo obr obu oc- oca ocb occ ock ocn oco ocr ocu oka okb okc okk oko okr oku on- ona onb onc onk onn ono onr onu oo- ooa oob ooc ook oon ooo oor or- ora orb orc ork orn oro orr oru ou- oua ouc ouk oun ouo our ra- raa rab rac rak ran rao rar rau rba rbb rbc rbk rbn rbo rbr rbu rca rcb rcc rcn rco rcr rcu rkb rkc rkk rko rku rna rnb rnc rnn rno rnr rnu roa rob roc rok ron roo ror rou rra rrb rrc rrk rrn rrr rru rua rub ruc ruk run ruo rur ruu ua- uaa uab uac uak uan uao uar uau uba ubb ubc ubk ubn ubo ubr ubu uca ucb ucc uck ucn uco ucr ucu uka ukb ukc ukk ukn ukr uku un- una unb unc unk unn uno unr unu uoa uob uoc uok uon uoo uor ur- ura urb urc urk urn uro urr uru uua uuc uun uur uuu