a-a a-b a-c aaa aab aac aao aas aau ab- aba abb abc abo abs abu ac- aca acb acc aco acs acu aoa aob aoc aoo aos aou as- asa asb asc aso ass asu au- aua aub auc auo aus b-u baa bab bac bao bas bau bba bbb bbc bbo bbs bbu bca bcb bcc bco bcs bcu boa bob boc boo bos bou bsa bsb bsc bso bss bsu bua bub buc buo bus buu c-- caa cab cac cao cas cau cba cbb cbc cbo cbs cbu cca ccb ccc cco ccs ccu co- coa cob coc coo cos cou csa csb csc cso css csu cua cub cuc cuo cus cuu oaa oab oac oao oas oau ob- oba obb obc obo obs obu oc- oca ocb occ oco ocs ocu oo- ooa oob ooc ooo oos os- osa osb osc oso oss osu ou- oua ouc ouo ous saa sab sac sao sas sau sba sbb sbc sbo sbs sbu sca scb scc sco scs scu soa sob soc soo sos sou ss- ssa ssb ssc sso sss ssu sua sub suc suo sus suu ua- uaa uab uac uao uas uau uba ubb ubc ubo ubs ubu uca ucb ucc uco ucs ucu uoa uob uoc uoo uos usa usb usc uso uss usu uua uuc uus uuu