-er a-a a-b a-c aaa aab aac aae aak aao aar aau ab- aba abb abc abe abk abo abr abu ac- aca acb acc ace ack aco acr acu aea aeb aec aee aek aeo aer aeu aka akb akc ake akk ako akr aku aoa aob aoc aoe aok aoo aor aou ar- ara arb arc are ark aro arr aru au- aua aub auc aue auk auo aur b-u baa bab bac bae bak bao bar bau bba bbb bbc bbe bbk bbo bbr bbu bca bcb bcc bce bck bco bcr bcu be- bea beb bec bee bek beo ber beu bka bkb bkc bke bkk bko bkr boa bob boc boe bok boo bor bou bra brb bre brk bro brr bru bua bub buc bue buk buo bur buu c-- caa cab cac cae cak cao car cau cba cbb cbc cbe cbk cbo cbr cbu cca ccb ccc cce cck cco ccr ccu ce- cea ceb cec cee cek ceo cer ceu cka ckb ckc cko co- coa cob coc coe cok coo cor cou cra crb crc cre crk cro crr cru cua cub cuc cue cuk cuo cur cuu eaa eab eac eae eak eao ear eau eba ebb ebc ebe ebk ebo ebr ebu ec- eca ecb ecc ece eck eco ecr ecu eea eeb eec eee eek eeo eer eka ekb ekc eke eko ekr eku eo- eoa eob eoc eoe eok eoo eor eou era erb erc ere erk ero err eru eu- eua eub euc eue eur ka- kaa kab kac kae kak kao kar kau kba kbb kbc kbe kbk kbo kbr kbu kca kcb kcc kce kck kcr kcu ke- kea keb kec kee kek keo ker kkb kkc kke kkk kkr kku koa kob koc koe kok koo kor kou kra krc krk kro krr kru kub kuc kue kuk kur kuu oaa oab oac oae oak oao oar oau ob- oba obb obc obe obk obo obr obu oc- oca ocb occ ock oco ocr ocu oea oeb oec oee oeo oer oka okb okc oke okk oko okr oku oo- ooa oob ooc ook ooo oor or- ora orb orc ore ork oro orr oru ou- oua ouc oue ouk ouo our ra- raa rab rac rae rak rao rar rau rba rbb rbc rbe rbk rbo rbr rbu rca rcb rcc rce rco rcr rcu re- rea reb rec ree rek reo rer reu rkb rkc rke rkk rko rku roa rob roc roe rok roo ror rou rra rrb rrc rrk rrr rru rua rub ruc rue ruk ruo rur ruu ua- uaa uab uac uae uak uao uar uau uba ubb ubc ube ubk ubo ubr ubu uca ucb ucc uce uck uco ucr ucu uea ueb uec uee uer uka ukb ukc uke ukk ukr uku uoa uob uoc uoe uok uoo uor ur- ura urb urc ure urk uro urr uru uua uuc uue uur uuu