-er a-a a-b aaa aab aae aao aap aar ab- aba abb abe abo abp abr aea aeb aee aeo aep aer aoa aob aoe aoo aop aor ap- apa apb ape apo app apr ar- ara arb are aro arp arr b-p baa bab bae bao bap bar bba bbb bbe bbo bbp bbr be- bea beb bee beo bep ber boa bob boe boo bop bor bpa bpb bpe bpo bpp bpr bra brb bre bro brp brr eaa eab eae eao eap ear eba ebb ebe ebo ebp ebr eea eeb eee eeo eep eer eo- eoa eob eoe eoo eop eor ep- epa epb epe epo epp epr era erb ere ero erp err oaa oab oae oao oap oar ob- oba obb obe obo obp obr oea oeb oee oeo oep oer oo- ooa oob ooo oop oor op- opa opb ope opo opp opr or- ora orb ore oro orp orr p-p paa pab pae pao pap par pba pbb pbe pbo pbp pbr pea peb pee peo pep per poa pob poe poo pop por ppa ppb ppe ppo ppp ppr pra prb pre pro prp prr ra- raa rab rae rao rap rar rba rbb rbe rbo rbp rbr re- rea reb ree reo rep rer roa rob roe roo rop ror rpa rpb rpe rpo rpp rpr rra rrb rrp rrr