a-a a-b a-c aaa aab aac aao aap aar aas ab- aba abb abc abo abp abr abs ac- aca acb acc aco acp acr acs aoa aob aoc aoo aop aor aos ap- apa apb apc apo app apr aps ar- ara arb arc aro arp arr ars as- asa asb asc aso asp asr ass b-p baa bab bac bao bap bar bas bba bbb bbc bbo bbp bbr bbs bca bcb bcc bco bcp bcr bcs boa bob boc boo bop bor bos bpa bpb bpc bpo bpp bpr bps bra brb bro brp brr brs bsa bsb bsc bso bsp bsr bss c-- caa cab cac cao cap car cas cba cbb cbc cbo cbp cbr cbs cca ccb ccc cco ccp ccr ccs co- coa cob coc coo cop cor cos cpa cpb cpc cpo cpp cpr cps cra crb crc cro crp crr crs csa csb csc cso csp csr css oaa oab oac oao oap oar oas ob- oba obb obc obo obp obr obs oc- oca ocb occ oco ocp ocr ocs oo- ooa oob ooc ooo oop oor oos op- opa opb opc opo opp opr ops or- ora orb orc oro orp orr ors os- osa osb osc oso osp osr oss p-p paa pab pac pao pap par pas pba pbb pbc pbo pbp pbr pbs pca pcb pcc pco pcp pcr pcs poa pob poc poo pop por pos ppa ppb ppc ppo ppp ppr pps pra prb prc pro prp prr prs ps- psa psb psc pso psp psr pss ra- raa rab rac rao rap rar ras rba rbb rbc rbo rbp rbr rbs rca rcb rcc rco rcp rcr rcs roa rob roc roo rop ror ros rpa rpb rpc rpo rpp rpr rps rra rrb rrc rrp rrr rrs rsa rsb rsc rso rsp rsr rss saa sab sac sao sap sar sas sba sbb sbc sbo sbp sbr sbs sca scb scc sco scp scr scs soa sob soc soo sop sor sos spa spb spc spo spp spr sps sr- sra srb src sro srp srr srs ss- ssa ssb ssc sso ssp ssr sss