a-a a-b aaa aab aak aap aar ab- aba abb abk abp abr aka akb akk akp akr ap- apa apb apk app apr ar- ara arb ark arp arr b-p baa bab bak bap bar bba bbb bbk bbp bbr bka bkb bkk bkp bkr bpa bpb bpp bpr bra brb brk brp brr ka- kaa kab kak kap kar kba kbb kbk kbp kbr kkb kkk kkp kkr kpa kpk kpp kpr kra krk krp krr p-p paa pab pak pap par pba pbb pbk pbp pbr pka pkb pkp pkr ppa ppb ppk ppp ppr pra prb prk prp prr ra- raa rab rak rap rar rba rbb rbk rbp rbr rkb rkk rkp rpa rpb rpk rpp rpr rra rrb rrk rrp rrr