a-a a-b aaa aab aam aar aas ab- aba abb abm abr abs ama amb amm amr ams ar- ara arb arm arr ars as- asa asb asm asr ass baa bab bam bar bas bba bbb bbm bbr bbs bma bmb bmm bmr bms bra brb brm brr brs bsa bsb bsm bsr bss m-r maa mab mam mar mas mba mbb mbm mbr mbs mma mmb mmm mmr mms mra mrb mrm mrr mrs msa msb msm msr mss ra- raa rab ram rar ras rba rbb rbm rbr rbs rma rmb rmm rmr rms rra rrb rrm rrr rrs rsa rsb rsm rsr rss saa sab sam sar sas sba sbb sbm sbr sbs sma smb smm smr sms sr- sra srb srm srr srs ss- ssa ssb ssm ssr sss