a-a a-b aaa aab aag aak aao aar ab- aba abb abg abk abo abr ag- aga agb agg agk ago agr aka akb akg akk ako akr aoa aob aog aok aoo aor ar- ara arb arg ark aro arr baa bab bag bak bao bar bba bbb bbg bbk bbo bbr bga bgb bgg bgk bgo bgr bka bkb bkg bkk bko bkr boa bob bog bok boo bor bra brb brg brk bro brr gaa gab gag gak gao gar gba gbg gbk gbo gbr gga ggb ggg ggo ggr gka gkb gko goa gob gog gok goo gor gra grb grg grk gro grr ka- kaa kab kag kak kao kar kba kbb kbk kbo kbr kga kgb kgo kkb kkk kkr koa kob kog kok koo kor kra krg krk kro krr oaa oab oag oak oao oar ob- oba obb obg obk obo obr oga ogg ogo oka okb okg okk oko okr oo- ooa oob oog ook ooo oor or- ora orb org ork oro orr ra- raa rab rag rak rao rar rba rbb rbg rbk rbo rbr rga rgb rgg rgk rgo rgr rkb rkg rkk rko roa rob rog rok roo ror rra rrb rrg rrk rrr