a-a a-b aaa aab aan aap aar ab- aba abb abn abp abr an- ana anb ann anp anr ap- apa apb apn app apr ar- ara arb arn arp arr b-p baa bab ban bap bar bba bbb bbn bbp bbr bna bnb bnn bnp bnr bpa bpb bpn bpp bpr bra brb brn brp brr naa nab nan nap nar nba nbb nbn nbp nbr nna nnb nnn nnp npa npb npn npp npr nra nrb nrn nrp nrr p-p paa pab pan pap par pba pbb pbn pbp pbr pn- pna pnb pnn pnp pnr ppa ppb ppn ppp ppr pra prb prn prp prr ra- raa rab ran rap rar rba rbb rbn rbp rbr rna rnb rnn rnp rnr rpa rpb rpn rpp rpr rra rrb rrn rrp rrr