a-a a-b a-c aaa aab aac aag aak aar ab- aba abb abc abg abk abr ac- aca acb acc acg ack acr ag- aga agb agc agg agk agr aka akb akc akg akk akr ar- ara arb arc arg ark arr baa bab bac bag bak bar bba bbb bbc bbg bbk bbr bca bcb bcc bcg bck bcr bga bgb bgc bgg bgk bgr bka bkb bkc bkg bkk bkr bra brb brg brk brr c-- caa cab cac cag cak car cba cbb cbc cbg cbk cbr cca ccb ccc ccg cck ccr cga cgb cgc cgg cgr cka ckb ckc cra crb crc crg crk crr gaa gab gac gag gak gar gba gbc gbg gbk gbr gca gcb gcc gcg gck gcr gga ggb ggc ggg ggr gka gkb gra grb grc grg grk grr ka- kaa kab kac kag kak kar kba kbb kbc kbk kbr kca kcb kcc kcg kck kcr kga kgb kgc kkb kkc kkk kkr kra krc krg krk krr ra- raa rab rac rag rak rar rba rbb rbc rbg rbk rbr rca rcb rcc rcg rcr rga rgb rgc rgg rgk rgr rkb rkc rkg rkk rra rrb rrc rrg rrk rrr