a-a a-b a-c aaa aab aac aae aaf aas ab- aba abb abc abe abf abs ac- aca acb acc ace acf acs aea aeb aec aee aef aes af- afa afb afc afe aff afs as- asa asb asc ase asf ass baa bab bac bae baf bas bba bbb bbc bbe bbf bbs bca bcb bcc bce bcf bcs be- bea beb bec bee bef bes bfa bfb bfc bfe bff bfs bsa bsb bsc bse bsf bss c-- caa cab cac cae caf cas cba cbb cbc cbe cbf cbs cca ccb ccc cce ccf ccs ce- cea ceb cec cee cef ces cfa cfb cfc cfe cff cfs csa csb csc cse csf css eaa eab eac eae eaf eas eba ebb ebc ebe ebf ebs ec- eca ecb ecc ece ecf ecs eea eeb eec eee eef ees ef- efa efb efc efe eff efs es- esa esb esc ese esf ess faa fab fac fae faf fas fba fbb fbc fbe fbf fbs fca fcb fcc fce fcf fcs fea feb fec fee fef fes ffa ffc ffe fff ffs fsa fsb fsc fse fsf fss saa sab sac sae saf sas sba sbb sbc sbe sbf sbs sca scb scc sce scf scs se- sea seb sec see sef ses sfa sfb sfc sfe sff sfs ss- ssa ssb ssc sse ssf sss