a-a a-b a-c aaa aab aac aad aar aau ab- aba abb abc abd abr abu ac- aca acb acc acd acr acu ad- ada adb adc add adr adu ar- ara arb arc ard arr aru au- aua aub auc aud aur b-u baa bab bac bad bar bau bba bbb bbc bbd bbr bbu bca bcb bcc bcd bcr bcu bda bdb bdc bdd bdr bdu bra brb brd brr bru bua bub buc bud bur buu c-- caa cab cac cad car cau cba cbb cbc cbd cbr cbu cca ccb ccc ccd ccr ccu cda cdb cdc cdd cdr cdu cra crb crc crd crr cru cua cub cuc cud cur cuu daa dab dac dad dar dau dba dbb dbc dbd dbr dbu dca dcb dcc dcd dcr dcu dda ddb ddc ddd ddr ddu dra drb drc drd drr dru dua dub duc dud dur ra- raa rab rac rad rar rau rba rbb rbc rbd rbr rbu rca rcb rcc rcd rcr rcu rda rdb rdc rdd rdr rdu rra rrb rrc rrd rrr rru rua rub ruc rud rur ruu ua- uaa uab uac uad uar uau uba ubb ubc ubr ubu uca ucb ucc ucd ucr ucu uda udb udc udd udr udu ur- ura urb urc urd urr uru uua uuc uur uuu