-er a-a a-b a-c a-t aaa aab aac aae aak aan aar aat ab- aba abb abc abe abk abn abr abt ac- aca acb acc ace ack acn acr act aea aeb aec aee aek aen aer aet aka akb akc ake akk akn akr an- ana anb anc ane ank ann anr ant ar- ara arb arc are ark arn arr art at- ata atb atc ate atn atr att baa bab bac bae bak ban bar bat bba bbb bbc bbe bbk bbn bbr bbt bca bcb bcc bce bck bcn bcr bct be- bea beb bec bee bek ben ber bet bka bkb bkc bke bkk bkn bkr bkt bna bnb bnc bne bnk bnn bnr bnt bra brb bre brk brn brr brt bta btb btc bte btk btn btr btt c-- caa cab cac cae cak can car cat cba cbb cbc cbe cbk cbn cbr cbt cca ccb ccc cce cck ccn ccr cct ce- cea ceb cec cee cek cen cer cet cka ckb ckc ckt cn- cna cnb cnc cne cnn cnr cnt cra crb crc cre crk crn crr crt cta ctb ctc cte ctk ctn ctr ctt eaa eab eac eae eak ean ear eat eba ebb ebc ebe ebk ebn ebr ebt ec- eca ecb ecc ece eck ecn ecr ect eea eeb eec eee eek een eer eet eka ekb ekc eke ekr ekt en- ena enb enc ene enk enn enr ent era erb erc ere erk ern err ert eta etb etc ete etk etn etr ett k-t ka- kaa kab kac kae kak kan kar kat kba kbb kbc kbe kbk kbn kbr kca kcb kcc kce kck kcn kcr kct ke- kea keb kec kee kek ken ker ket kkb kkc kke kkk kkn kkr kkt kn- kna knc kne knk knn knr knt kra krc krk krn krr krt kta ktb ktc kte ktk ktn ktr ktt naa nab nac nae nak nan nar nat nba nbb nbc nbe nbk nbn nbr nbt nca ncb ncc nce nck ncn ncr nct ne- nea neb nec nee nek nen ner net nka nkc nke nkk nkn nkr nkt nna nnb nnc nne nnk nnn nnt nra nrb nrc nre nrk nrn nrr nrt nta ntb ntc nte ntk ntn ntr ntt ra- raa rab rac rae rak ran rar rat rba rbb rbc rbe rbk rbn rbr rbt rca rcb rcc rce rcn rcr rct re- rea reb rec ree rek ren rer ret rkb rkc rke rkk rkt rna rnb rnc rnn rnr rnt rra rrb rrc rrk rrn rrr rrt rta rtb rtc rte rtk rtn rtr rtt taa tab tac tae tak tan tar tat tba tbb tbc tbe tbk tbn tbr tbt tca tcb tcc tce tck tcn tcr tct te- tea teb tec tee tek ten ter tet tka tkb tkc tke tkk tkr tkt tna tnb tnc tne tnk tnn tnr tnt tra trb trc tre trk trn trr trt tta ttb ttc tte ttk ttn ttr ttt