a-a a-b a-c aaa aab aac aar aas aau ab- aba abb abc abr abs abu ac- aca acb acc acr acs acu ar- ara arb arc arr ars aru as- asa asb asc asr ass asu au- aua aub auc aur aus b-u baa bab bac bar bas bau bba bbb bbc bbr bbs bbu bca bcb bcc bcr bcs bcu bra brb brr brs bru bsa bsb bsc bsr bss bsu bua bub buc bur bus buu c-- caa cab cac car cas cau cba cbb cbc cbr cbs cbu cca ccb ccc ccr ccs ccu cra crb crc crr crs cru csa csb csc csr css csu cua cub cuc cur cus cuu ra- raa rab rac rar ras rau rba rbb rbc rbr rbs rbu rca rcb rcc rcr rcs rcu rra rrb rrc rrr rrs rru rsa rsb rsc rsr rss rsu rua rub ruc rur rus ruu saa sab sac sar sas sau sba sbb sbc sbr sbs sbu sca scb scc scr scs scu sr- sra srb src srr srs ss- ssa ssb ssc ssr sss ssu sua sub suc sur sus suu ua- uaa uab uac uar uas uau uba ubb ubc ubr ubs ubu uca ucb ucc ucr ucs ucu ur- ura urb urc urr urs uru usa usb usc usr uss usu uua uuc uur uus uuu