a-a a-b a-t aaa aab aam aar aat ab- aba abb abm abr abt ama amb amm amr amt ar- ara arb arm arr art at- ata atb atm atr att baa bab bam bar bat bba bbb bbm bbr bbt bma bmb bmm bmr bmt bra brb brm brr brt bta btb btm btr btt m-r maa mab mam mar mat mba mbb mbm mbr mbt mma mmb mmm mmr mmt mra mrb mrm mrr mrt mta mtb mtm mtr mtt ra- raa rab ram rar rat rba rbb rbm rbr rbt rma rmb rmm rmr rmt rra rrb rrm rrr rrt rta rtb rtm rtr rtt taa tab tam tar tat tba tbb tbm tbr tbt tma tmb tmm tmr tmt tra trb trm trr trt tta ttb ttm ttr ttt