-er a-a a-b a-c a-t aaa aab aac aae aan aar aat ab- aba abb abc abe abn abr abt ac- aca acb acc ace acn acr act aea aeb aec aee aen aer aet an- ana anb anc ane ann anr ant ar- ara arb arc are arn arr art at- ata atb atc ate atn atr att baa bab bac bae ban bar bat bba bbb bbc bbe bbn bbr bbt bca bcb bcc bce bcn bcr bct be- bea beb bec bee ben ber bet bna bnb bnc bne bnn bnr bnt bra brb bre brn brr brt bta btb btc bte btn btr btt c-- caa cab cac cae can car cat cba cbb cbc cbe cbn cbr cbt cca ccb ccc cce ccn ccr cct ce- cea ceb cec cee cen cer cet cn- cna cnb cnc cne cnn cnr cnt cra crb crc cre crn crr crt cta ctb ctc cte ctn ctr ctt eaa eab eac eae ean ear eat eba ebb ebc ebe ebn ebr ebt ec- eca ecb ecc ece ecn ecr ect eea eeb eec eee een eer eet en- ena enb enc ene enn enr ent era erb erc ere ern err ert eta etb etc ete etn etr ett naa nab nac nae nan nar nat nba nbb nbc nbe nbn nbr nbt nca ncb ncc nce ncn ncr nct ne- nea neb nec nee nen ner net nna nnb nnc nne nnn nnt nra nrb nrc nre nrn nrr nrt nta ntb ntc nte ntn ntr ntt ra- raa rab rac rae ran rar rat rba rbb rbc rbe rbn rbr rbt rca rcb rcc rce rcn rcr rct re- rea reb rec ree ren rer ret rna rnb rnc rnn rnr rnt rra rrb rrc rrn rrr rrt rta rtb rtc rte rtn rtr rtt taa tab tac tae tan tar tat tba tbb tbc tbe tbn tbr tbt tca tcb tcc tce tcn tcr tct te- tea teb tec tee ten ter tet tna tnb tnc tne tnn tnr tnt tra trb trc tre trn trr trt tta ttb ttc tte ttn ttr ttt