-ic a-a a-b a-c a-i aaa aab aac aai aak aao aar aas ab- aba abb abc abi abk abo abr abs ac- aca acb acc aci ack aco acr acs ai- aia aib aic aii aik aio air ais aka akb akc aki akk ako akr aks aoa aob aoc aoi aok aoo aor aos ar- ara arb arc ari ark aro arr ars as- asa asb asc asi ask aso asr ass baa bab bac bai bak bao bar bas bba bbb bbc bbi bbk bbo bbr bbs bca bcb bcc bci bck bco bcr bcs bi- bia bib bic bii bik bio bir bis bka bkb bkc bkk bko bkr bks boa bob boc boi bok boo bor bos bra brb bri brk bro brr brs bsa bsb bsc bsi bsk bso bsr bss c-- caa cab cac cai cak cao car cas cba cbb cbc cbi cbk cbo cbr cbs cca ccb ccc cci cck cco ccr ccs ci- cia cib cic cii cik cio cir cis cka ckb ckc cki cko cks co- coa cob coc coi cok coo cor cos cra crb crc cri crk cro crr crs csa csb csc csi csk cso csr css ia- iaa iab iac iai iao iar ias iba ibb ibc ibi ibk ibo ibr ibs ica icb icc ici ick ico icr ics iia iib iic iii iio iir iis ika ikb ikc iki ikk iko ikr iks io- ioa iob ioc ioi ioo ior ios ir- ira irb irc iri irk iro irr irs is- isa isb isc isi isk iso isr iss ka- kaa kab kac kai kak kao kar kas kba kbb kbc kbi kbk kbo kbr kbs kca kcb kcc kci kck kcr kcs kia kib kic kii kik kio kir kis kkb kkc kki kkk kkr kks koa kob koc koi kok koo kor kos kra krc kri krk kro krr krs ksa ksb ksc ksi ksk kso ksr kss o-i oaa oab oac oai oak oao oar oas ob- oba obb obc obi obk obo obr obs oc- oca ocb occ oci ock oco ocr ocs oia oib oic oii oik oio oir ois oka okb okc oki okk oko okr oks oo- ooa oob ooc ooi ook ooo oor oos or- ora orb orc ori ork oro orr ors os- osa osb osc osi osk oso osr oss ra- raa rab rac rai rak rao rar ras rba rbb rbc rbi rbk rbo rbr rbs rca rcb rcc rci rco rcr rcs ria rib ric rii rik rio rir ris rkb rkc rkk rko rks roa rob roc roi rok roo ror ros rra rrb rrc rri rrk rrr rrs rsa rsb rsc rsi rsk rso rsr rss saa sab sac sai sak sao sar sas sba sbb sbc sbi sbk sbo sbr sbs sca scb scc sci sck sco scr scs sia sib sic sii sik sio sir sis sk- ska skb skc ski skk sko skr sks soa sob soc soi sok soo sor sos sr- sra srb src sri srk sro srr srs ss- ssa ssb ssc ssi ssk sso ssr sss