a-a a-b a-t aaa aab aao aar aat aau ab- aba abb abo abr abt abu aoa aob aoo aor aot aou ar- ara arb aro arr art aru at- ata atb ato atr att atu au- aua aub auo aur aut b-u baa bab bao bar bat bau bba bbb bbo bbr bbt bbu boa bob boo bor bot bou bra brb bro brr brt bru bta btb bto btr btt btu bua bub buo bur but buu oaa oab oao oar oat oau ob- oba obb obo obr obt obu oo- ooa oob ooo oor oot or- ora orb oro orr ort oru ot- ota otb oto otr ott otu ou- oua ouo our out ra- raa rab rao rar rat rau rba rbb rbo rbr rbt rbu roa rob roo ror rot rou rra rrb rrr rrt rru rta rtb rto rtr rtt rtu rua rub ruo rur rut ruu taa tab tao tar tat tau tba tbb tbo tbr tbt tbu to- toa tob too tor tot tou tra trb tro trr trt tru tta ttb tto ttr ttt ttu tua tub tuo tur tut tuu ua- uaa uab uao uar uat uau uba ubb ubo ubr ubt ubu uoa uob uoo uor uot ur- ura urb uro urr urt uru uta utb uto utr utt utu uua uur uut uuu