a-a a-b a-t aaa aab aak aar aat ab- aba abb abk abr abt aka akb akk akr ar- ara arb ark arr art at- ata atb atr att baa bab bak bar bat bba bbb bbk bbr bbt bka bkb bkk bkr bkt bra brb brk brr brt bta btb btk btr btt k-t ka- kaa kab kak kar kat kba kbb kbk kbr kkb kkk kkr kkt kra krk krr krt kta ktb ktk ktr ktt ra- raa rab rak rar rat rba rbb rbk rbr rbt rkb rkk rkt rra rrb rrk rrr rrt rta rtb rtk rtr rtt taa tab tak tar tat tba tbb tbk tbr tbt tka tkb tkk tkr tkt tra trb trk trr trt tta ttb ttk ttr ttt