-er a-a a-b a-c aaa aab aac aae aan aao aap aar aas ab- aba abb abc abe abn abo abp abr abs ac- aca acb acc ace acn aco acp acr acs aea aeb aec aee aen aeo aep aer aes an- ana anb anc ane ann ano anp anr ans aoa aob aoc aoe aon aoo aop aor aos ap- apa apb apc ape apn apo app apr aps ar- ara arb arc are arn aro arp arr ars as- asa asb asc ase asn aso asp asr ass b-p baa bab bac bae ban bao bap bar bas bba bbb bbc bbe bbn bbo bbp bbr bbs bca bcb bcc bce bcn bco bcp bcr bcs be- bea beb bec bee ben beo bep ber bes bna bnb bnc bne bnn bno bnp bnr bns boa bob boc boe bon boo bop bor bos bpa bpb bpc bpe bpn bpo bpp bpr bps bra brb bre brn bro brp brr brs bsa bsb bsc bse bsn bso bsp bsr bss c-- caa cab cac cae can cao cap car cas cba cbb cbc cbe cbn cbo cbp cbr cbs cca ccb ccc cce ccn cco ccp ccr ccs ce- cea ceb cec cee cen ceo cep cer ces cn- cna cnb cnc cne cnn cno cnp cnr cns co- coa cob coc coe con coo cop cor cos cpa cpb cpc cpe cpn cpo cpp cpr cps cra crb crc cre crn cro crp crr crs csa csb csc cse csn cso csp csr css eaa eab eac eae ean eao eap ear eas eba ebb ebc ebe ebn ebo ebp ebr ebs ec- eca ecb ecc ece ecn eco ecr ecs eea eeb eec eee een eeo eep eer ees en- ena enb enc ene enn eno enp enr ens eo- eoa eob eoc eoe eon eoo eop eor eos ep- epa epb epc epe epn epo epp epr eps era erb erc ere ern ero erp err ers es- esa esb esc ese esn eso esp esr ess naa nab nac nae nan nao nap nar nas nba nbb nbc nbe nbn nbo nbp nbr nbs nca ncb ncc nce ncn nco ncp ncr ncs ne- nea neb nec nee nen neo nep ner nes nna nnb nnc nne nnn nno nnp nns no- noa nob noc noe non noo nop nor nos npa npb npc npe npn npo npp npr nps nra nrb nrc nre nrn nro nrp nrr nrs nsa nsb nsc nse nsn nso nsp nsr nss oaa oab oac oae oan oao oap oar oas ob- oba obb obc obe obn obo obp obr obs oc- oca ocb occ ocn oco ocp ocr ocs oea oeb oec oee oen oeo oep oer oes on- ona onb onc one onn ono onp onr ons oo- ooa oob ooc oon ooo oop oor oos op- opa opb opc ope opn opo opp opr ops or- ora orb orc ore orn oro orp orr ors os- osa osb osc ose osn oso osp osr oss p-p paa pab pac pae pan pao pap par pas pba pbb pbc pbe pbn pbo pbp pbr pbs pca pcb pcc pce pcn pco pcp pcr pcs pea peb pec pee pen peo pep per pes pn- pna pnb pnc pne pnn pno pnp pnr pns poa pob poc poe pon poo pop por pos ppa ppb ppc ppe ppn ppo ppp ppr pps pra prb prc pre prn pro prp prr prs ps- psa psb psc pse psn pso psp psr pss ra- raa rab rac rae ran rao rap rar ras rba rbb rbc rbe rbn rbo rbp rbr rbs rca rcb rcc rce rcn rco rcp rcr rcs re- rea reb rec ree ren reo rep rer res rna rnb rnc rnn rno rnp rnr rns roa rob roc roe ron roo rop ror ros rpa rpb rpc rpe rpn rpo rpp rpr rps rra rrb rrc rrn rrp rrr rrs rsa rsb rsc rse rsn rso rsp rsr rss saa sab sac sae san sao sap sar sas sba sbb sbc sbe sbn sbo sbp sbr sbs sca scb scc sce scn sco scp scr scs se- sea seb sec see sen seo sep ser ses sna snb snc sne snn sno snp snr sns soa sob soc soe son soo sop sor sos spa spb spc spe spn spo spp spr sps sr- sra srb src sre srn sro srp srr srs ss- ssa ssb ssc sse ssn sso ssp ssr sss