a-a a-b a-t aaa aab aas aat aau ab- aba abb abs abt abu as- asa asb ass ast asu at- ata atb ats att atu au- aua aub aus aut b-u baa bab bas bat bau bba bbb bbs bbt bbu bsa bsb bss bst bsu bta btb bts btt btu bua bub bus but buu saa sab sas sat sau sba sbb sbs sbt sbu ss- ssa ssb sss sst ssu sta stb sts stt stu sua sub sus sut suu taa tab tas tat tau tba tbb tbs tbt tbu tsa tsb tss tst tsu tta ttb tts ttt ttu tua tub tus tut tuu ua- uaa uab uas uat uau uba ubb ubs ubt ubu usa usb uss ust usu uta utb uts utt utu uua uus uut uuu