-er a-a a-b aaa aab aae aan aap aar ab- aba abb abe abn abp abr aea aeb aee aen aep aer an- ana anb ane ann anp anr ap- apa apb ape apn app apr ar- ara arb are arn arp arr b-p baa bab bae ban bap bar bba bbb bbe bbn bbp bbr be- bea beb bee ben bep ber bna bnb bne bnn bnp bnr bpa bpb bpe bpn bpp bpr bra brb bre brn brp brr eaa eab eae ean eap ear eba ebb ebe ebn ebp ebr eea eeb eee een eep eer en- ena enb ene enn enp enr ep- epa epb epe epn epp epr era erb ere ern erp err naa nab nae nan nap nar nba nbb nbe nbn nbp nbr ne- nea neb nee nen nep ner nna nnb nne nnn nnp npa npb npe npn npp npr nra nrb nre nrn nrp nrr p-p paa pab pae pan pap par pba pbb pbe pbn pbp pbr pea peb pee pen pep per pn- pna pnb pne pnn pnp pnr ppa ppb ppe ppn ppp ppr pra prb pre prn prp prr ra- raa rab rae ran rap rar rba rbb rbe rbn rbp rbr re- rea reb ree ren rep rer rna rnb rnn rnp rnr rpa rpb rpe rpn rpp rpr rra rrb rrn rrp rrr