a-a a-b a-c aaa aab aac aad aao aap ab- aba abb abc abd abo abp ac- aca acb acc acd aco acp ad- ada adb adc add ado adp aoa aob aoc aod aoo aop ap- apa apb apc apd apo app b-p baa bab bac bad bao bap bba bbb bbc bbd bbo bbp bca bcb bcc bcd bco bcp bda bdb bdc bdd bdo bdp boa bob boc bod boo bop bpa bpb bpc bpd bpo bpp c-- caa cab cac cad cao cap cba cbb cbc cbd cbo cbp cca ccb ccc ccd cco ccp cda cdb cdc cdd cdo cdp co- coa cob coc cod coo cop cpa cpb cpc cpd cpo cpp daa dab dac dad dao dap dba dbb dbc dbd dbo dbp dca dcb dcc dcd dco dcp dda ddb ddc ddd ddo ddp doa dob doc dod doo dop dpa dpb dpc dpd dpo dpp oaa oab oac oad oao oap ob- oba obb obc obd obo obp oc- oca ocb occ ocd oco ocp oda odb odc odd odo odp oo- ooa oob ooc ood ooo oop op- opa opb opc opd opo opp p-p paa pab pac pad pao pap pba pbb pbc pbd pbo pbp pca pcb pcc pcd pco pcp pda pdb pdc pdd pdo pdp poa pob poc pod poo pop ppa ppb ppc ppd ppo ppp