a-a a-b aaa aab aae aam aas ab- aba abb abe abm abs aea aeb aee aem aes ama amb ame amm ams as- asa asb ase asm ass baa bab bae bam bas bba bbb bbe bbm bbs be- bea beb bee bem bes bma bmb bme bmm bms bsa bsb bse bsm bss eaa eab eae eam eas eba ebb ebe ebm ebs eea eeb eee eem ees em- ema emb eme emm ems es- esa esb ese esm ess maa mab mae mam mas mba mbb mbe mbm mbs mea meb mee mem mes mma mmb mme mmm mms msa msb mse msm mss saa sab sae sam sas sba sbb sbe sbm sbs se- sea seb see sem ses sma smb sme smm sms ss- ssa ssb sse ssm sss