a-a a-b aaa aab aam aar aax ab- aba abb abm abr abx ama amb amm amr amx ar- ara arb arm arr arx ax- axa axm axr axx baa bab bam bar bax bba bbb bbm bbr bbx bma bmb bmm bmr bmx bra brb brm brr brx bxb bxm bxx m-r maa mab mam mar max mba mbb mbm mbr mbx mma mmb mmm mmr mmx mra mrb mrm mrr mrx mxa mxr ra- raa rab ram rar rax rba rbb rbm rbr rbx rma rmb rmm rmr rmx rra rrb rrm rrr rxr xaa xam xar xbr xbx xma xmm xmr xmx xrx xxx