-er a-a a-b aaa aab aae aao aap aar aax ab- aba abb abe abo abp abr abx aea aeb aee aeo aep aer aex aoa aob aoe aoo aop aor aox ap- apa apb ape apo app apr apx ar- ara arb are aro arp arr arx ax- axa axe axo axp axr axx b-p baa bab bae bao bap bar bax bba bbb bbe bbo bbp bbr bbx be- bea beb bee beo bep ber bex boa bob boe boo bop bor box bpa bpb bpe bpo bpp bpr bpx bra brb bre bro brp brr brx bxb bxo bxx eaa eab eae eao eap ear eax eba ebb ebe ebo ebp ebr ebx eea eeb eee eeo eep eer eex eo- eoa eob eoe eoo eop eor ep- epa epb epe epo epp epr epx era erb ere ero erp err ex- exa exe exo exp exr exx oaa oab oae oao oap oar oax ob- oba obb obe obo obp obr obx oea oeb oee oeo oep oer oex oo- ooa oob ooo oop oor oox op- opa opb ope opo opp opr opx or- ora orb ore oro orp orr orx ox- oxa oxb oxo oxx p-p paa pab pae pao pap par pax pba pbb pbe pbo pbp pbr pbx pea peb pee peo pep per pex poa pob poe poo pop por pox ppa ppb ppe ppo ppp ppr ppx pra prb pre pro prp prr prx pxe pxr ra- raa rab rae rao rap rar rax rba rbb rbe rbo rbp rbr rbx re- rea reb ree reo rep rer rex roa rob roe roo rop ror rox rpa rpb rpe rpo rpp rpr rpx rra rrb rrp rrr rxp rxr xaa xap xar xbe xbr xbx xee xep xer xex xoa xoo xop xor xox xpa xpb xpe xpo xpp xrx xxo xxp xxx