a-a a-b a-t aaa aab aao aap aar aas aat ab- aba abb abo abp abr abs abt aoa aob aoo aop aor aos aot ap- apa apb apo app apr aps apt ar- ara arb aro arp arr ars art as- asa asb aso asp asr ass ast at- ata atb ato atp atr ats att b-p baa bab bao bap bar bas bat bba bbb bbo bbp bbr bbs bbt boa bob boo bop bor bos bot bpa bpb bpo bpp bpr bps bpt bra brb bro brp brr brs brt bsa bsb bso bsp bsr bss bst bta btb bto btp btr bts btt oaa oab oao oap oar oas oat ob- oba obb obo obp obr obs obt oo- ooa oob ooo oop oor oos oot op- opa opb opo opp opr ops opt or- ora orb oro orp orr ors ort os- osa osb oso osp osr oss ost ot- ota otb oto otp otr ots ott p-p paa pab pao pap par pas pat pba pbb pbo pbp pbr pbs pbt poa pob poo pop por pos pot ppa ppb ppo ppp ppr pps ppt pra prb pro prp prr prs prt ps- psa psb pso psp psr pss pst pt- pta ptb pto ptp ptr pts ptt ra- raa rab rao rap rar ras rat rba rbb rbo rbp rbr rbs rbt roa rob roo rop ror ros rot rpa rpb rpo rpp rpr rps rpt rra rrb rrp rrr rrs rrt rsa rsb rso rsp rsr rss rst rta rtb rto rtp rtr rts rtt saa sab sao sap sar sas sat sba sbb sbo sbp sbr sbs sbt soa sob soo sop sor sos sot spa spb spo spp spr sps spt sr- sra srb sro srp srr srs srt ss- ssa ssb sso ssp ssr sss sst sta stb sto stp str sts stt taa tab tao tap tar tas tat tba tbb tbo tbp tbr tbs tbt to- toa tob too top tor tos tot tpa tpb tpo tpp tpr tps tpt tra trb tro trp trr trs trt tsa tsb tso tsp tsr tss tst tta ttb tto ttp ttr tts ttt