a-a a-b a-c aaa aab aac aam aao aas ab- aba abb abc abm abo abs ac- aca acb acc acm aco acs ama amb amc amm amo ams aoa aob aoc aom aoo aos as- asa asb asc asm aso ass baa bab bac bam bao bas bba bbb bbc bbm bbo bbs bca bcb bcc bcm bco bcs bma bmb bmc bmm bmo bms boa bob boc bom boo bos bsa bsb bsc bsm bso bss c-- caa cab cac cam cao cas cba cbb cbc cbm cbo cbs cca ccb ccc ccm cco ccs cma cmb cmc cmm cmo cms co- coa cob coc com coo cos csa csb csc csm cso css m-o maa mab mac mam mao mas mba mbb mbc mbm mbo mbs mc- mca mcb mcc mcm mco mcs mma mmb mmc mmm mmo mms moa mob moc mom moo mos msa msb msc msm mso mss oaa oab oac oam oao oas ob- oba obb obc obm obo obs oc- oca ocb occ ocm oco ocs om- oma omb omc omm omo oms oo- ooa oob ooc oom ooo oos os- osa osb osc osm oso oss saa sab sac sam sao sas sba sbb sbc sbm sbo sbs sca scb scc scm sco scs sma smb smc smm smo sms soa sob soc som soo sos ss- ssa ssb ssc ssm sso sss