-er a-a a-b a-c aaa aab aac aae aao aap aar ab- aba abb abc abe abo abp abr ac- aca acb acc ace aco acp acr aea aeb aec aee aeo aep aer aoa aob aoc aoe aoo aop aor ap- apa apb apc ape apo app apr ar- ara arb arc are aro arp arr b-p baa bab bac bae bao bap bar bba bbb bbc bbe bbo bbp bbr bca bcb bcc bce bco bcp bcr be- bea beb bec bee beo bep ber boa bob boc boe boo bop bor bpa bpb bpc bpe bpo bpp bpr bra brb bre bro brp brr c-- caa cab cac cae cao cap car cba cbb cbc cbe cbo cbp cbr cca ccb ccc cce cco ccp ccr ce- cea ceb cec cee ceo cep cer co- coa cob coc coe coo cop cor cpa cpb cpc cpe cpo cpp cpr cra crb crc cre cro crp crr eaa eab eac eae eao eap ear eba ebb ebc ebe ebo ebp ebr ec- eca ecb ecc ece eco ecr eea eeb eec eee eeo eep eer eo- eoa eob eoc eoe eoo eop eor ep- epa epb epc epe epo epp epr era erb erc ere ero erp err oaa oab oac oae oao oap oar ob- oba obb obc obe obo obp obr oc- oca ocb occ oco ocp ocr oea oeb oec oee oeo oep oer oo- ooa oob ooc ooo oop oor op- opa opb opc ope opo opp opr or- ora orb orc ore oro orp orr p-p paa pab pac pae pao pap par pba pbb pbc pbe pbo pbp pbr pca pcb pcc pce pco pcp pcr pea peb pec pee peo pep per poa pob poc poe poo pop por ppa ppb ppc ppe ppo ppp ppr pra prb prc pre pro prp prr ra- raa rab rac rae rao rap rar rba rbb rbc rbe rbo rbp rbr rca rcb rcc rce rco rcp rcr re- rea reb rec ree reo rep rer roa rob roc roe roo rop ror rpa rpb rpc rpe rpo rpp rpr rra rrb rrc rrp rrr