a-a a-b a-i aaa aab aai aao aap aar aas ab- aba abb abi abo abp abr abs ai- aia aib aii aio aip air ais aoa aob aoi aoo aop aor aos ap- apa apb api apo app apr aps ar- ara arb ari aro arp arr ars as- asa asb asi aso asp asr ass b-p baa bab bai bao bap bar bas bba bbb bbi bbo bbp bbr bbs bi- bia bib bii bio bip bir bis boa bob boi boo bop bor bos bpa bpb bpi bpo bpp bpr bps bra brb bri bro brp brr brs bsa bsb bsi bso bsp bsr bss ia- iaa iab iai iao iap iar ias iba ibb ibi ibo ibp ibr ibs iia iib iii iio iip iir iis io- ioa iob ioi ioo iop ior ios ipa ipb ipi ipo ipp ipr ips ir- ira irb iri iro irp irr irs is- isa isb isi iso isp isr iss o-i oaa oab oai oao oap oar oas ob- oba obb obi obo obp obr obs oia oib oii oio oip oir ois oo- ooa oob ooi ooo oop oor oos op- opa opb opi opo opp opr ops or- ora orb ori oro orp orr ors os- osa osb osi oso osp osr oss p-p paa pab pai pao pap par pas pba pbb pbi pbo pbp pbr pbs pia pib pii pio pip pir pis poa pob poi poo pop por pos ppa ppb ppi ppo ppp ppr pps pra prb pri pro prp prr prs ps- psa psb psi pso psp psr pss ra- raa rab rai rao rap rar ras rba rbb rbi rbo rbp rbr rbs ria rib rii rio rip rir ris roa rob roi roo rop ror ros rpa rpb rpi rpo rpp rpr rps rra rrb rri rrp rrr rrs rsa rsb rsi rso rsp rsr rss saa sab sai sao sap sar sas sba sbb sbi sbo sbp sbr sbs sia sib sii sio sip sir sis soa sob soi soo sop sor sos spa spb spi spo spp spr sps sr- sra srb sri sro srp srr srs ss- ssa ssb ssi sso ssp ssr sss