a-a a-b aaa aab aam aao aas ab- aba abb abm abo abs ama amb amm amo ams aoa aob aom aoo aos as- asa asb asm aso ass baa bab bam bao bas bba bbb bbm bbo bbs bma bmb bmm bmo bms boa bob bom boo bos bsa bsb bsm bso bss m-o maa mab mam mao mas mba mbb mbm mbo mbs mma mmb mmm mmo mms moa mob mom moo mos msa msb msm mso mss oaa oab oam oao oas ob- oba obb obm obo obs om- oma omb omm omo oms oo- ooa oob oom ooo oos os- osa osb osm oso oss saa sab sam sao sas sba sbb sbm sbo sbs sma smb smm smo sms soa sob som soo sos ss- ssa ssb ssm sso sss