-er a-a a-b a-c aaa aab aac aae aan aao aap aar ab- aba abb abc abe abn abo abp abr ac- aca acb acc ace acn aco acp acr aea aeb aec aee aen aeo aep aer an- ana anb anc ane ann ano anp anr aoa aob aoc aoe aon aoo aop aor ap- apa apb apc ape apn apo app apr ar- ara arb arc are arn aro arp arr b-p baa bab bac bae ban bao bap bar bba bbb bbc bbe bbn bbo bbp bbr bca bcb bcc bce bcn bco bcp bcr be- bea beb bec bee ben beo bep ber bna bnb bnc bne bnn bno bnp bnr boa bob boc boe bon boo bop bor bpa bpb bpc bpe bpn bpo bpp bpr bra brb bre brn bro brp brr c-- caa cab cac cae can cao cap car cba cbb cbc cbe cbn cbo cbp cbr cca ccb ccc cce ccn cco ccp ccr ce- cea ceb cec cee cen ceo cep cer cn- cna cnb cnc cne cnn cno cnp cnr co- coa cob coc coe con coo cop cor cpa cpb cpc cpe cpn cpo cpp cpr cra crb crc cre crn cro crp crr eaa eab eac eae ean eao eap ear eba ebb ebc ebe ebn ebo ebp ebr ec- eca ecb ecc ece ecn eco ecr eea eeb eec eee een eeo eep eer en- ena enb enc ene enn eno enp enr eo- eoa eob eoc eoe eon eoo eop eor ep- epa epb epc epe epn epo epp epr era erb erc ere ern ero erp err naa nab nac nae nan nao nap nar nba nbb nbc nbe nbn nbo nbp nbr nca ncb ncc nce ncn nco ncp ncr ne- nea neb nec nee nen neo nep ner nna nnb nnc nne nnn nno nnp no- noa nob noc noe non noo nop nor npa npb npc npe npn npo npp npr nra nrb nrc nre nrn nro nrp nrr oaa oab oac oae oan oao oap oar ob- oba obb obc obe obn obo obp obr oc- oca ocb occ ocn oco ocp ocr oea oeb oec oee oen oeo oep oer on- ona onb onc one onn ono onp onr oo- ooa oob ooc oon ooo oop oor op- opa opb opc ope opn opo opp opr or- ora orb orc ore orn oro orp orr p-p paa pab pac pae pan pao pap par pba pbb pbc pbe pbn pbo pbp pbr pca pcb pcc pce pcn pco pcp pcr pea peb pec pee pen peo pep per pn- pna pnb pnc pne pnn pno pnp pnr poa pob poc poe pon poo pop por ppa ppb ppc ppe ppn ppo ppp ppr pra prb prc pre prn pro prp prr ra- raa rab rac rae ran rao rap rar rba rbb rbc rbe rbn rbo rbp rbr rca rcb rcc rce rcn rco rcp rcr re- rea reb rec ree ren reo rep rer rna rnb rnc rnn rno rnp rnr roa rob roc roe ron roo rop ror rpa rpb rpc rpe rpn rpo rpp rpr rra rrb rrc rrn rrp rrr