a-a a-b a-t aaa aab aak aao aas aat ab- aba abb abk abo abs abt aka akb akk ako aks aoa aob aok aoo aos aot as- asa asb ask aso ass ast at- ata atb ato ats att baa bab bak bao bas bat bba bbb bbk bbo bbs bbt bka bkb bkk bko bks bkt boa bob bok boo bos bot bsa bsb bsk bso bss bst bta btb btk bto bts btt k-t ka- kaa kab kak kao kas kat kba kbb kbk kbo kbs kkb kkk kks kkt koa kob kok koo kos kot ksa ksb ksk kso kss kst kta ktb ktk kto kts ktt oaa oab oak oao oas oat ob- oba obb obk obo obs obt oka okb okk oko oks oo- ooa oob ook ooo oos oot os- osa osb osk oso oss ost ot- ota otb otk oto ots ott saa sab sak sao sas sat sba sbb sbk sbo sbs sbt sk- ska skb skk sko sks skt soa sob sok soo sos sot ss- ssa ssb ssk sso sss sst sta stb stk sto sts stt taa tab tak tao tas tat tba tbb tbk tbo tbs tbt tka tkb tkk tko tks tkt to- toa tob tok too tos tot tsa tsb tsk tso tss tst tta ttb ttk tto tts ttt