a-a a-b a-c aaa aab aac aak aao aar aas aau ab- aba abb abc abk abo abr abs abu ac- aca acb acc ack aco acr acs acu aka akb akc akk ako akr aks aku aoa aob aoc aok aoo aor aos aou ar- ara arb arc ark aro arr ars aru as- asa asb asc ask aso asr ass asu au- aua aub auc auk auo aur aus b-u baa bab bac bak bao bar bas bau bba bbb bbc bbk bbo bbr bbs bbu bca bcb bcc bck bco bcr bcs bcu bka bkb bkc bkk bko bkr bks boa bob boc bok boo bor bos bou bra brb brk bro brr brs bru bsa bsb bsc bsk bso bsr bss bsu bua bub buc buk buo bur bus buu c-- caa cab cac cak cao car cas cau cba cbb cbc cbk cbo cbr cbs cbu cca ccb ccc cck cco ccr ccs ccu cka ckb ckc cko cks co- coa cob coc cok coo cor cos cou cra crb crc crk cro crr crs cru csa csb csc csk cso csr css csu cua cub cuc cuk cuo cur cus cuu ka- kaa kab kac kak kao kar kas kau kba kbb kbc kbk kbo kbr kbs kbu kca kcb kcc kck kcr kcs kcu kkb kkc kkk kkr kks kku koa kob koc kok koo kor kos kou kra krc krk kro krr krs kru ksa ksb ksc ksk kso ksr kss ksu kub kuc kuk kur kus kuu oaa oab oac oak oao oar oas oau ob- oba obb obc obk obo obr obs obu oc- oca ocb occ ock oco ocr ocs ocu oka okb okc okk oko okr oks oku oo- ooa oob ooc ook ooo oor oos or- ora orb orc ork oro orr ors oru os- osa osb osc osk oso osr oss osu ou- oua ouc ouk ouo our ous ra- raa rab rac rak rao rar ras rau rba rbb rbc rbk rbo rbr rbs rbu rca rcb rcc rco rcr rcs rcu rkb rkc rkk rko rks rku roa rob roc rok roo ror ros rou rra rrb rrc rrk rrr rrs rru rsa rsb rsc rsk rso rsr rss rsu rua rub ruc ruk ruo rur rus ruu saa sab sac sak sao sar sas sau sba sbb sbc sbk sbo sbr sbs sbu sca scb scc sck sco scr scs scu sk- ska skb skc skk sko skr sks sku soa sob soc sok soo sor sos sou sr- sra srb src srk sro srr srs ss- ssa ssb ssc ssk sso ssr sss ssu sua sub suc suk suo sur sus suu ua- uaa uab uac uak uao uar uas uau uba ubb ubc ubk ubo ubr ubs ubu uca ucb ucc uck uco ucr ucs ucu uka ukb ukc ukk ukr uku uoa uob uoc uok uoo uor uos ur- ura urb urc urk uro urr urs uru usa usb usc usk uso usr uss usu uua uuc uur uus uuu