a-a a-b a-c aaa aab aac aaf aao aas aau ab- aba abb abc abf abo abs abu ac- aca acb acc acf aco acs acu af- afa afb afc aff afo afs afu aoa aob aoc aof aoo aos aou as- asa asb asc asf aso ass asu au- aua aub auc auf auo aus b-u baa bab bac baf bao bas bau bba bbb bbc bbf bbo bbs bbu bca bcb bcc bcf bco bcs bcu bfa bfb bfc bff bfo bfs bfu boa bob boc bof boo bos bou bsa bsb bsc bsf bso bss bsu bua bub buc buf buo bus buu c-- caa cab cac caf cao cas cau cba cbb cbc cbf cbo cbs cbu cca ccb ccc ccf cco ccs ccu cfa cfb cfc cff cfo cfs cfu co- coa cob coc cof coo cos cou csa csb csc csf cso css csu cua cub cuc cuf cuo cus cuu faa fab fac faf fao fas fau fba fbb fbc fbf fbo fbs fbu fca fcb fcc fcf fco fcs fcu ffa ffc fff ffo ffs ffu foa fob foc fof foo fos fou fsa fsb fsc fsf fso fss fsu fua fub fuf fuo fus fuu oaa oab oac oaf oao oas oau ob- oba obb obc obf obo obs obu oc- oca ocb occ ocf oco ocs ocu of- ofa ofb ofc off ofo ofs ofu oo- ooa oob ooc oof ooo oos os- osa osb osc osf oso oss osu ou- oua ouc ouf ouo ous saa sab sac saf sao sas sau sba sbb sbc sbf sbo sbs sbu sca scb scc scf sco scs scu sfa sfb sfc sff sfo sfs sfu soa sob soc sof soo sos sou ss- ssa ssb ssc ssf sso sss ssu sua sub suc suf suo sus suu ua- uaa uab uac uaf uao uas uau uba ubb ubc ubf ubo ubs ubu uca ucb ucc ucf uco ucs ucu ufa ufc uff ufo ufs ufu uoa uob uoc uoo uos usa usb usc usf uso uss usu uua uuc uus uuu