-ic a-a a-b a-c a-i aaa aab aac aai aao aap ab- aba abb abc abi abo abp ac- aca acb acc aci aco acp ai- aia aib aic aii aio aip aoa aob aoc aoi aoo aop ap- apa apb apc api apo app b-p baa bab bac bai bao bap bba bbb bbc bbi bbo bbp bca bcb bcc bci bco bcp bi- bia bib bic bii bio bip boa bob boc boi boo bop bpa bpb bpc bpi bpo bpp c-- caa cab cac cai cao cap cba cbb cbc cbi cbo cbp cca ccb ccc cci cco ccp ci- cia cib cic cii cio cip co- coa cob coc coi coo cop cpa cpb cpc cpi cpo cpp ia- iaa iab iac iai iao iap iba ibb ibc ibi ibo ibp ica icb icc ici ico icp iia iib iic iii iio iip io- ioa iob ioc ioi ioo iop ipa ipb ipc ipi ipo ipp o-i oaa oab oac oai oao oap ob- oba obb obc obi obo obp oc- oca ocb occ oci oco ocp oia oib oic oii oio oip oo- ooa oob ooc ooi ooo oop op- opa opb opc opi opo opp p-p paa pab pac pai pao pap pba pbb pbc pbi pbo pbp pca pcb pcc pci pco pcp pia pib pic pii pio pip poa pob poc poi poo pop ppa ppb ppc ppi ppo ppp