-er a-a a-b a-c aaa aab aac aae aak aar ab- aba abb abc abe abk abr ac- aca acb acc ace ack acr aea aeb aec aee aek aer aka akb akc ake akk akr ar- ara arb arc are ark arr baa bab bac bae bak bar bba bbb bbc bbe bbk bbr bca bcb bcc bce bck bcr be- bea beb bec bee bek ber bka bkb bkc bke bkk bkr bra brb bre brk brr c-- caa cab cac cae cak car cba cbb cbc cbe cbk cbr cca ccb ccc cce cck ccr ce- cea ceb cec cee cek cer cka ckb ckc cra crb crc cre crk crr eaa eab eac eae eak ear eba ebb ebc ebe ebk ebr ec- eca ecb ecc ece eck ecr eea eeb eec eee eek eer eka ekb ekc eke ekr era erb erc ere erk err ka- kaa kab kac kae kak kar kba kbb kbc kbe kbk kbr kca kcb kcc kce kck kcr ke- kea keb kec kee kek ker kkb kkc kke kkk kkr kra krc krk krr ra- raa rab rac rae rak rar rba rbb rbc rbe rbk rbr rca rcb rcc rce rcr re- rea reb rec ree rek rer rkb rkc rke rkk rra rrb rrc rrk rrr