a-a a-b a-t aaa aab aan aao aas aat ab- aba abb abn abo abs abt an- ana anb ann ano ans ant aoa aob aon aoo aos aot as- asa asb asn aso ass ast at- ata atb atn ato ats att baa bab ban bao bas bat bba bbb bbn bbo bbs bbt bna bnb bnn bno bns bnt boa bob bon boo bos bot bsa bsb bsn bso bss bst bta btb btn bto bts btt naa nab nan nao nas nat nba nbb nbn nbo nbs nbt nna nnb nnn nno nns nnt no- noa nob non noo nos not nsa nsb nsn nso nss nst nta ntb ntn nto nts ntt oaa oab oan oao oas oat ob- oba obb obn obo obs obt on- ona onb onn ono ons ont oo- ooa oob oon ooo oos oot os- osa osb osn oso oss ost ot- ota otb otn oto ots ott saa sab san sao sas sat sba sbb sbn sbo sbs sbt sna snb snn sno sns snt soa sob son soo sos sot ss- ssa ssb ssn sso sss sst sta stb stn sto sts stt taa tab tan tao tas tat tba tbb tbn tbo tbs tbt tna tnb tnn tno tns tnt to- toa tob ton too tos tot tsa tsb tsn tso tss tst tta ttb ttn tto tts ttt