-er a-a a-b a-c a-t aaa aab aac aae aak aar aat ab- aba abb abc abe abk abr abt ac- aca acb acc ace ack acr act aea aeb aec aee aek aer aet aka akb akc ake akk akr ar- ara arb arc are ark arr art at- ata atb atc ate atr att baa bab bac bae bak bar bat bba bbb bbc bbe bbk bbr bbt bca bcb bcc bce bck bcr bct be- bea beb bec bee bek ber bet bka bkb bkc bke bkk bkr bkt bra brb bre brk brr brt bta btb btc bte btk btr btt c-- caa cab cac cae cak car cat cba cbb cbc cbe cbk cbr cbt cca ccb ccc cce cck ccr cct ce- cea ceb cec cee cek cer cet cka ckb ckc ckt cra crb crc cre crk crr crt cta ctb ctc cte ctk ctr ctt eaa eab eac eae eak ear eat eba ebb ebc ebe ebk ebr ebt ec- eca ecb ecc ece eck ecr ect eea eeb eec eee eek eer eet eka ekb ekc eke ekr ekt era erb erc ere erk err ert eta etb etc ete etk etr ett k-t ka- kaa kab kac kae kak kar kat kba kbb kbc kbe kbk kbr kca kcb kcc kce kck kcr kct ke- kea keb kec kee kek ker ket kkb kkc kke kkk kkr kkt kra krc krk krr krt kta ktb ktc kte ktk ktr ktt ra- raa rab rac rae rak rar rat rba rbb rbc rbe rbk rbr rbt rca rcb rcc rce rcr rct re- rea reb rec ree rek rer ret rkb rkc rke rkk rkt rra rrb rrc rrk rrr rrt rta rtb rtc rte rtk rtr rtt taa tab tac tae tak tar tat tba tbb tbc tbe tbk tbr tbt tca tcb tcc tce tck tcr tct te- tea teb tec tee tek ter tet tka tkb tkc tke tkk tkr tkt tra trb trc tre trk trr trt tta ttb ttc tte ttk ttr ttt