a-a a-b aaa aab aao aar aau aax ab- aba abb abo abr abu abx aoa aob aoo aor aou aox ar- ara arb aro arr aru arx au- aua aub auo aur aux ax- axa axo axr axx b-u baa bab bao bar bau bax bba bbb bbo bbr bbu bbx boa bob boo bor bou box bra brb bro brr bru brx bua bub buo bur buu bux bxb bxo bxx oaa oab oao oar oau oax ob- oba obb obo obr obu obx oo- ooa oob ooo oor oox or- ora orb oro orr oru orx ou- oua ouo our ox- oxa oxb oxo oxx ra- raa rab rao rar rau rax rba rbb rbo rbr rbu rbx roa rob roo ror rou rox rra rrb rrr rru rua rub ruo rur ruu rux rxr ua- uaa uab uao uar uau uba ubb ubo ubr ubu ubx uoa uob uoo uor uox ur- ura urb uro urr uru urx uua uur uuu uxb uxo uxr uxu xaa xar xau xbr xbx xoa xoo xor xox xrx xxo xxx