a-a a-b a-c aaa aab aac aao aar aas aau ab- aba abb abc abo abr abs abu ac- aca acb acc aco acr acs acu aoa aob aoc aoo aor aos aou ar- ara arb arc aro arr ars aru as- asa asb asc aso asr ass asu au- aua aub auc auo aur aus b-u baa bab bac bao bar bas bau bba bbb bbc bbo bbr bbs bbu bca bcb bcc bco bcr bcs bcu boa bob boc boo bor bos bou bra brb bro brr brs bru bsa bsb bsc bso bsr bss bsu bua bub buc buo bur bus buu c-- caa cab cac cao car cas cau cba cbb cbc cbo cbr cbs cbu cca ccb ccc cco ccr ccs ccu co- coa cob coc coo cor cos cou cra crb crc cro crr crs cru csa csb csc cso csr css csu cua cub cuc cuo cur cus cuu oaa oab oac oao oar oas oau ob- oba obb obc obo obr obs obu oc- oca ocb occ oco ocr ocs ocu oo- ooa oob ooc ooo oor oos or- ora orb orc oro orr ors oru os- osa osb osc oso osr oss osu ou- oua ouc ouo our ous ra- raa rab rac rao rar ras rau rba rbb rbc rbo rbr rbs rbu rca rcb rcc rco rcr rcs rcu roa rob roc roo ror ros rou rra rrb rrc rrr rrs rru rsa rsb rsc rso rsr rss rsu rua rub ruc ruo rur rus ruu saa sab sac sao sar sas sau sba sbb sbc sbo sbr sbs sbu sca scb scc sco scr scs scu soa sob soc soo sor sos sou sr- sra srb src sro srr srs ss- ssa ssb ssc sso ssr sss ssu sua sub suc suo sur sus suu ua- uaa uab uac uao uar uas uau uba ubb ubc ubo ubr ubs ubu uca ucb ucc uco ucr ucs ucu uoa uob uoc uoo uor uos ur- ura urb urc uro urr urs uru usa usb usc uso usr uss usu uua uuc uur uus uuu