-er a-a a-b aaa aab aae aak aan aao aap aar ab- aba abb abe abk abn abo abp abr aea aeb aee aek aen aeo aep aer aka akb ake akk akn ako akp akr an- ana anb ane ank ann ano anp anr aoa aob aoe aok aon aoo aop aor ap- apa apb ape apk apn apo app apr ar- ara arb are ark arn aro arp arr b-p baa bab bae bak ban bao bap bar bba bbb bbe bbk bbn bbo bbp bbr be- bea beb bee bek ben beo bep ber bka bkb bke bkk bkn bko bkp bkr bna bnb bne bnk bnn bno bnp bnr boa bob boe bok bon boo bop bor bpa bpb bpe bpn bpo bpp bpr bra brb bre brk brn bro brp brr eaa eab eae eak ean eao eap ear eba ebb ebe ebk ebn ebo ebp ebr eea eeb eee eek een eeo eep eer eka ekb eke eko ekp ekr en- ena enb ene enk enn eno enp enr eo- eoa eob eoe eok eon eoo eop eor ep- epa epb epe epn epo epp epr era erb ere erk ern ero erp err ka- kaa kab kae kak kan kao kap kar kba kbb kbe kbk kbn kbo kbp kbr ke- kea keb kee kek ken keo kep ker kkb kke kkk kkn kkp kkr kn- kna kne knk knn kno knp knr koa kob koe kok kon koo kop kor kpa kpe kpk kpn kpo kpp kpr kra krk krn kro krp krr naa nab nae nak nan nao nap nar nba nbb nbe nbk nbn nbo nbp nbr ne- nea neb nee nek nen neo nep ner nka nke nkk nkn nko nkp nkr nna nnb nne nnk nnn nno nnp no- noa nob noe nok non noo nop nor npa npb npe npn npo npp npr nra nrb nre nrk nrn nro nrp nrr oaa oab oae oak oan oao oap oar ob- oba obb obe obk obn obo obp obr oea oeb oee oen oeo oep oer oka okb oke okk oko okp okr on- ona onb one onk onn ono onp onr oo- ooa oob ook oon ooo oop oor op- opa opb ope opk opn opo opp opr or- ora orb ore ork orn oro orp orr p-p paa pab pae pak pan pao pap par pba pbb pbe pbk pbn pbo pbp pbr pea peb pee pek pen peo pep per pka pkb pke pkn pko pkp pkr pn- pna pnb pne pnk pnn pno pnp pnr poa pob poe pok pon poo pop por ppa ppb ppe ppk ppn ppo ppp ppr pra prb pre prk prn pro prp prr ra- raa rab rae rak ran rao rap rar rba rbb rbe rbk rbn rbo rbp rbr re- rea reb ree rek ren reo rep rer rkb rke rkk rko rkp rna rnb rnn rno rnp rnr roa rob roe rok ron roo rop ror rpa rpb rpe rpk rpn rpo rpp rpr rra rrb rrk rrn rrp rrr