-er a-a a-b aaa aab aae aan aao aap aar aax ab- aba abb abe abn abo abp abr abx aea aeb aee aen aeo aep aer aex an- ana anb ane ann ano anp anr anx aoa aob aoe aon aoo aop aor aox ap- apa apb ape apn apo app apr apx ar- ara arb are arn aro arp arr arx ax- axa axe axn axo axp axr axx b-p baa bab bae ban bao bap bar bax bba bbb bbe bbn bbo bbp bbr bbx be- bea beb bee ben beo bep ber bex bna bnb bne bnn bno bnp bnr bnx boa bob boe bon boo bop bor box bpa bpb bpe bpn bpo bpp bpr bpx bra brb bre brn bro brp brr brx bxb bxn bxo bxx eaa eab eae ean eao eap ear eax eba ebb ebe ebn ebo ebp ebr ebx eea eeb eee een eeo eep eer eex en- ena enb ene enn eno enp enr eo- eoa eob eoe eon eoo eop eor ep- epa epb epe epn epo epp epr epx era erb ere ern ero erp err ex- exa exe exo exp exr exx naa nab nae nan nao nap nar nax nba nbb nbe nbn nbo nbp nbr nbx ne- nea neb nee nen neo nep ner nex nna nnb nne nnn nno nnp no- noa nob noe non noo nop nor nox npa npb npe npn npo npp npr nra nrb nre nrn nro nrp nrr nrx oaa oab oae oan oao oap oar oax ob- oba obb obe obn obo obp obr obx oea oeb oee oen oeo oep oer oex on- ona onb one onn ono onp onr onx oo- ooa oob oon ooo oop oor oox op- opa opb ope opn opo opp opr opx or- ora orb ore orn oro orp orr orx ox- oxa oxb oxn oxo oxx p-p paa pab pae pan pao pap par pax pba pbb pbe pbn pbo pbp pbr pbx pea peb pee pen peo pep per pex pn- pna pnb pne pnn pno pnp pnr pnx poa pob poe pon poo pop por pox ppa ppb ppe ppn ppo ppp ppr ppx pra prb pre prn pro prp prr prx pxe pxr ra- raa rab rae ran rao rap rar rax rba rbb rbe rbn rbo rbp rbr rbx re- rea reb ree ren reo rep rer rex rna rnb rnn rno rnp rnr roa rob roe ron roo rop ror rox rpa rpb rpe rpn rpo rpp rpr rpx rra rrb rrn rrp rrr rxp rxr xaa xan xap xar xbe xbr xbx xee xen xep xer xex xna xno xoa xon xoo xop xor xox xpa xpb xpe xpn xpo xpp xrx xxo xxp xxx