a-a a-b a-c aaa aab aac aak aao aap aar aas ab- aba abb abc abk abo abp abr abs ac- aca acb acc ack aco acp acr acs aka akb akc akk ako akp akr aks aoa aob aoc aok aoo aop aor aos ap- apa apb apc apk apo app apr aps ar- ara arb arc ark aro arp arr ars as- asa asb asc ask aso asp asr ass b-p baa bab bac bak bao bap bar bas bba bbb bbc bbk bbo bbp bbr bbs bca bcb bcc bck bco bcp bcr bcs bka bkb bkc bkk bko bkp bkr bks boa bob boc bok boo bop bor bos bpa bpb bpc bpo bpp bpr bps bra brb brk bro brp brr brs bsa bsb bsc bsk bso bsp bsr bss c-- caa cab cac cak cao cap car cas cba cbb cbc cbk cbo cbp cbr cbs cca ccb ccc cck cco ccp ccr ccs cka ckb ckc cko cks co- coa cob coc cok coo cop cor cos cpa cpb cpc cpk cpo cpp cpr cps cra crb crc crk cro crp crr crs csa csb csc csk cso csp csr css ka- kaa kab kac kak kao kap kar kas kba kbb kbc kbk kbo kbp kbr kbs kca kcb kcc kck kcp kcr kcs kkb kkc kkk kkp kkr kks koa kob koc kok koo kop kor kos kpa kpc kpk kpo kpp kpr kps kra krc krk kro krp krr krs ksa ksb ksc ksk kso ksp ksr kss oaa oab oac oak oao oap oar oas ob- oba obb obc obk obo obp obr obs oc- oca ocb occ ock oco ocp ocr ocs oka okb okc okk oko okp okr oks oo- ooa oob ooc ook ooo oop oor oos op- opa opb opc opk opo opp opr ops or- ora orb orc ork oro orp orr ors os- osa osb osc osk oso osp osr oss p-p paa pab pac pak pao pap par pas pba pbb pbc pbk pbo pbp pbr pbs pca pcb pcc pck pco pcp pcr pcs pka pkb pkc pko pkp pkr pks poa pob poc pok poo pop por pos ppa ppb ppc ppk ppo ppp ppr pps pra prb prc prk pro prp prr prs ps- psa psb psc psk pso psp psr pss ra- raa rab rac rak rao rap rar ras rba rbb rbc rbk rbo rbp rbr rbs rca rcb rcc rco rcp rcr rcs rkb rkc rkk rko rkp rks roa rob roc rok roo rop ror ros rpa rpb rpc rpk rpo rpp rpr rps rra rrb rrc rrk rrp rrr rrs rsa rsb rsc rsk rso rsp rsr rss saa sab sac sak sao sap sar sas sba sbb sbc sbk sbo sbp sbr sbs sca scb scc sck sco scp scr scs sk- ska skb skc skk sko skp skr sks soa sob soc sok soo sop sor sos spa spb spc spk spo spp spr sps sr- sra srb src srk sro srp srr srs ss- ssa ssb ssc ssk sso ssp ssr sss