a-a a-b a-c aaa aab aac aak aar aay ab- aba abb abc abk abr aby ac- aca acb acc ack acr acy aka akb akc akk akr ar- ara arb arc ark arr ary ay- aya ayc ayk ayr baa bab bac bak bar bay bba bbb bbc bbk bbr bby bca bcb bcc bck bcr bcy bka bkb bkc bkk bkr bra brb brk brr bry by- bya byc byk byr c-- caa cab cac cak car cay cba cbb cbc cbk cbr cby cca ccb ccc cck ccr cka ckb ckc cky cra crb crc crk crr cry cya cyb cyc cyk cyr ka- kaa kab kac kak kar kay kba kbb kbc kbk kbr kca kcb kcc kck kcr kkb kkc kkk kkr kky kra krc krk krr kry kya kyc kyr ra- raa rab rac rak rar ray rba rbb rbc rbk rbr rca rcb rcc rcr rkb rkc rkk rky rra rrb rrc rrk rrr ry- rya ryc ryk ryr ryy yaa yab yac yak yar yay ybc ybr yby yca ycc ycy yka ykk yra yrc yyb yyc yyy