-er a-a a-b a-c aaa aab aac aae aar aas ab- aba abb abc abe abr abs ac- aca acb acc ace acr acs aea aeb aec aee aer aes ar- ara arb arc are arr ars as- asa asb asc ase asr ass baa bab bac bae bar bas bba bbb bbc bbe bbr bbs bca bcb bcc bce bcr bcs be- bea beb bec bee ber bes bra brb bre brr brs bsa bsb bsc bse bsr bss c-- caa cab cac cae car cas cba cbb cbc cbe cbr cbs cca ccb ccc cce ccr ccs ce- cea ceb cec cee cer ces cra crb crc cre crr crs csa csb csc cse csr css eaa eab eac eae ear eas eba ebb ebc ebe ebr ebs ec- eca ecb ecc ece ecr ecs eea eeb eec eee eer ees era erb erc ere err ers es- esa esb esc ese esr ess ra- raa rab rac rae rar ras rba rbb rbc rbe rbr rbs rca rcb rcc rce rcr rcs re- rea reb rec ree rer res rra rrb rrc rrr rrs rsa rsb rsc rse rsr rss saa sab sac sae sar sas sba sbb sbc sbe sbr sbs sca scb scc sce scr scs se- sea seb sec see ser ses sr- sra srb src sre srr srs ss- ssa ssb ssc sse ssr sss