a-a a-b a-t aaa aab aas aat aau aax ab- aba abb abs abt abu abx as- asa asb ass ast asu asx at- ata atb ats att atu atx au- aua aub aus aut aux ax- axa axs axt axx b-u baa bab bas bat bau bax bba bbb bbs bbt bbu bbx bsa bsb bss bst bsu bsx bta btb bts btt btu btx bua bub bus but buu bux bxb bxx saa sab sas sat sau sax sba sbb sbs sbt sbu sbx ss- ssa ssb sss sst ssu ssx sta stb sts stt stu stx sua sub sus sut suu sux sxs sxt sxu t-x taa tab tas tat tau tax tba tbb tbs tbt tbu tsa tsb tss tst tsu tsx tta ttb tts ttt ttu ttx tua tub tus tut tuu tux txs txt txu ua- uaa uab uas uat uau uba ubb ubs ubt ubu ubx usa usb uss ust usu usx uta utb uts utt utu utx uua uus uut uuu uxb uxt uxu xaa xas xat xau xbx xsa xsb xss xst xts xtx xus xxx