a-a a-b aaa aab aar aau aav ab- aba abb abr abu abv ar- ara arb arr aru arv au- aua aub aur auv av- ava avb avr avu b-u baa bab bar bau bav bba bbb bbr bbu bra brb brr bru brv bua bub bur buu bva bvb bvr bvu bvv ra- raa rab rar rau rav rba rbb rbr rbu rra rrb rrr rru rua rub rur ruu ruv rva rvb rvr rvu rvv ua- uaa uab uar uau uav uba ubb ubr ubu ubv ur- ura urb urr uru uua uur uuu uva uvb uvu uvv v-a vaa vab var vau vav vba vbr vbv vra vrb vrr vru vur vuv vva vvb vvr vvv