a-a a-b a-c aaa aab aac aak aan aar ab- aba abb abc abk abn abr ac- aca acb acc ack acn acr aka akb akc akk akn akr an- ana anb anc ank ann anr ar- ara arb arc ark arn arr baa bab bac bak ban bar bba bbb bbc bbk bbn bbr bca bcb bcc bck bcn bcr bka bkb bkc bkk bkn bkr bna bnb bnc bnk bnn bnr bra brb brk brn brr c-- caa cab cac cak can car cba cbb cbc cbk cbn cbr cca ccb ccc cck ccn ccr cka ckb ckc cn- cna cnb cnc cnn cnr cra crb crc crk crn crr ka- kaa kab kac kak kan kar kba kbb kbc kbk kbn kbr kca kcb kcc kck kcn kcr kkb kkc kkk kkn kkr kn- kna knc knk knn knr kra krc krk krn krr naa nab nac nak nan nar nba nbb nbc nbk nbn nbr nca ncb ncc nck ncn ncr nka nkc nkk nkn nkr nna nnb nnc nnk nnn nra nrb nrc nrk nrn nrr ra- raa rab rac rak ran rar rba rbb rbc rbk rbn rbr rca rcb rcc rcn rcr rkb rkc rkk rna rnb rnc rnn rnr rra rrb rrc rrk rrn rrr