a-a a-b a-i aaa aab aai aao aap ab- aba abb abi abo abp ai- aia aib aii aio aip aoa aob aoi aoo aop ap- apa apb api apo app b-p baa bab bai bao bap bba bbb bbi bbo bbp bi- bia bib bii bio bip boa bob boi boo bop bpa bpb bpi bpo bpp ia- iaa iab iai iao iap iba ibb ibi ibo ibp iia iib iii iio iip io- ioa iob ioi ioo iop ipa ipb ipi ipo ipp o-i oaa oab oai oao oap ob- oba obb obi obo obp oia oib oii oio oip oo- ooa oob ooi ooo oop op- opa opb opi opo opp p-p paa pab pai pao pap pba pbb pbi pbo pbp pia pib pii pio pip poa pob poi poo pop ppa ppb ppi ppo ppp