a-a a-b a-i aaa aab aai aak aar aax ab- aba abb abi abk abr abx ai- aia aib aii aik air aix aka akb aki akk akr ar- ara arb ari ark arr arx ax- axa axi axk axr axx baa bab bai bak bar bax bba bbb bbi bbk bbr bbx bi- bia bib bii bik bir bix bka bkb bkk bkr bkx bra brb bri brk brr brx bxb bxi bxx ia- iaa iab iai iar iba ibb ibi ibk ibr ibx iia iib iii iir iix ika ikb iki ikk ikr ikx ir- ira irb iri irk irr irx ixi ka- kaa kab kai kak kar kax kba kbb kbi kbk kbr kbx kia kib kii kik kir kix kkb kki kkk kkr kra kri krk krr ra- raa rab rai rak rar rax rba rbb rbi rbk rbr rbx ria rib rii rik rir rix rkb rkk rra rrb rri rrk rrr rxr xaa xak xar xbr xbx xia xii xix xkb xrx xxi xxx