-ic a-a a-b a-c a-i aaa aab aac aai aao aas ab- aba abb abc abi abo abs ac- aca acb acc aci aco acs ai- aia aib aic aii aio ais aoa aob aoc aoi aoo aos as- asa asb asc asi aso ass baa bab bac bai bao bas bba bbb bbc bbi bbo bbs bca bcb bcc bci bco bcs bi- bia bib bic bii bio bis boa bob boc boi boo bos bsa bsb bsc bsi bso bss c-- caa cab cac cai cao cas cba cbb cbc cbi cbo cbs cca ccb ccc cci cco ccs ci- cia cib cic cii cio cis co- coa cob coc coi coo cos csa csb csc csi cso css ia- iaa iab iac iai iao ias iba ibb ibc ibi ibo ibs ica icb icc ici ico ics iia iib iic iii iio iis io- ioa iob ioc ioi ioo ios is- isa isb isc isi iso iss o-i oaa oab oac oai oao oas ob- oba obb obc obi obo obs oc- oca ocb occ oci oco ocs oia oib oic oii oio ois oo- ooa oob ooc ooi ooo oos os- osa osb osc osi oso oss saa sab sac sai sao sas sba sbb sbc sbi sbo sbs sca scb scc sci sco scs sia sib sic sii sio sis soa sob soc soi soo sos ss- ssa ssb ssc ssi sso sss