a-a a-b a-c aaa aab aac aak aao aar aau ab- aba abb abc abk abo abr abu ac- aca acb acc ack aco acr acu aka akb akc akk ako akr aku aoa aob aoc aok aoo aor aou ar- ara arb arc ark aro arr aru au- aua aub auc auk auo aur b-u baa bab bac bak bao bar bau bba bbb bbc bbk bbo bbr bbu bca bcb bcc bck bco bcr bcu bka bkb bkc bkk bko bkr boa bob boc bok boo bor bou bra brb brk bro brr bru bua bub buc buk buo bur buu c-- caa cab cac cak cao car cau cba cbb cbc cbk cbo cbr cbu cca ccb ccc cck cco ccr ccu cka ckb ckc cko co- coa cob coc cok coo cor cou cra crb crc crk cro crr cru cua cub cuc cuk cuo cur cuu ka- kaa kab kac kak kao kar kau kba kbb kbc kbk kbo kbr kbu kca kcb kcc kck kcr kcu kkb kkc kkk kkr kku koa kob koc kok koo kor kou kra krc krk kro krr kru kub kuc kuk kur kuu oaa oab oac oak oao oar oau ob- oba obb obc obk obo obr obu oc- oca ocb occ ock oco ocr ocu oka okb okc okk oko okr oku oo- ooa oob ooc ook ooo oor or- ora orb orc ork oro orr oru ou- oua ouc ouk ouo our ra- raa rab rac rak rao rar rau rba rbb rbc rbk rbo rbr rbu rca rcb rcc rco rcr rcu rkb rkc rkk rko rku roa rob roc rok roo ror rou rra rrb rrc rrk rrr rru rua rub ruc ruk ruo rur ruu ua- uaa uab uac uak uao uar uau uba ubb ubc ubk ubo ubr ubu uca ucb ucc uck uco ucr ucu uka ukb ukc ukk ukr uku uoa uob uoc uok uoo uor ur- ura urb urc urk uro urr uru uua uuc uur uuu