a-a a-b a-c aaa aab aac aaf aah ab- aba abb abc abf abh ac- aca acb acc acf ach af- afa afb afc aff afh aha ahb ahc ahf ahh baa bab bac baf bah bba bbb bbc bbf bbh bca bcb bcc bcf bch bfa bfb bfc bff bfh bha bhb bhc bhf bhh c-- caa cab cac caf cah cba cbb cbc cbf cbh cca ccb ccc ccf cch cfa cfb cfc cff cfh ch- cha chb chc chf chh faa fab fac faf fah fba fbb fbc fbf fbh fca fcb fcc fcf ffa ffc fff ffh fha fhb fhc fhf fhh haa hab hac haf hah hba hbb hbc hbf hbh hca hcb hcc hcf hch hfa hfb hfc hff hfh hha hhb hhc hhf hhh