a-a a-b aaa aab aak aao aap aar ab- aba abb abk abo abp abr aka akb akk ako akp akr aoa aob aok aoo aop aor ap- apa apb apk apo app apr ar- ara arb ark aro arp arr b-p baa bab bak bao bap bar bba bbb bbk bbo bbp bbr bka bkb bkk bko bkp bkr boa bob bok boo bop bor bpa bpb bpo bpp bpr bra brb brk bro brp brr ka- kaa kab kak kao kap kar kba kbb kbk kbo kbp kbr kkb kkk kkp kkr koa kob kok koo kop kor kpa kpk kpo kpp kpr kra krk kro krp krr oaa oab oak oao oap oar ob- oba obb obk obo obp obr oka okb okk oko okp okr oo- ooa oob ook ooo oop oor op- opa opb opk opo opp opr or- ora orb ork oro orp orr p-p paa pab pak pao pap par pba pbb pbk pbo pbp pbr pka pkb pko pkp pkr poa pob pok poo pop por ppa ppb ppk ppo ppp ppr pra prb prk pro prp prr ra- raa rab rak rao rap rar rba rbb rbk rbo rbp rbr rkb rkk rko rkp roa rob rok roo rop ror rpa rpb rpk rpo rpp rpr rra rrb rrk rrp rrr