-th a-a a-c a-t aaa aac aah aat aax ac- aca acc ach act acx aha ahc ahh aht ahx at- ata atc ath att atx ax- axa axh axt axx c-- caa cac cah cat cax cca ccc cch cct ccx ch- cha chc chh cht chx cta ctc cth ctt ctx cxc cxh cxt cxx haa hac hah hat hax hca hcc hch hct hha hhc hhh hht hta htc hth htt htx hxc t-x taa tac tah tat tax tca tcc tch tct tcx th- tha thc thh tht thx tta ttc tth ttt ttx txt xaa xac xat xch xcx xht xtc xtx xxx