a-a a-b a-i aaa aab aai aao aap aar ab- aba abb abi abo abp abr ai- aia aib aii aio aip air aoa aob aoi aoo aop aor ap- apa apb api apo app apr ar- ara arb ari aro arp arr b-p baa bab bai bao bap bar bba bbb bbi bbo bbp bbr bi- bia bib bii bio bip bir boa bob boi boo bop bor bpa bpb bpi bpo bpp bpr bra brb bri bro brp brr ia- iaa iab iai iao iap iar iba ibb ibi ibo ibp ibr iia iib iii iio iip iir io- ioa iob ioi ioo iop ior ipa ipb ipi ipo ipp ipr ir- ira irb iri iro irp irr o-i oaa oab oai oao oap oar ob- oba obb obi obo obp obr oia oib oii oio oip oir oo- ooa oob ooi ooo oop oor op- opa opb opi opo opp opr or- ora orb ori oro orp orr p-p paa pab pai pao pap par pba pbb pbi pbo pbp pbr pia pib pii pio pip pir poa pob poi poo pop por ppa ppb ppi ppo ppp ppr pra prb pri pro prp prr ra- raa rab rai rao rap rar rba rbb rbi rbo rbp rbr ria rib rii rio rip rir roa rob roi roo rop ror rpa rpb rpi rpo rpp rpr rra rrb rri rrp rrr