a-a a-b a-t aaa aab aad aaf aao aar aat ab- aba abb abd abf abo abr abt ad- ada adb add adf ado adr adt af- afa afb afd aff afo afr aft aoa aob aod aof aoo aor aot ar- ara arb ard arf aro arr art at- ata atb atd atf ato atr att baa bab bad baf bao bar bat bba bbb bbd bbf bbo bbr bbt bda bdb bdd bdf bdo bdr bdt bfa bfb bfd bff bfo bfr bft boa bob bod bof boo bor bot bra brb brd brf bro brr brt bta btb btd btf bto btr btt daa dab dad daf dao dar dat dba dbb dbd dbf dbo dbr dbt dda ddb ddd ddf ddo ddr ddt dfa dfb dfd dff dfo dfr dft doa dob dod dof doo dor dot dra drb drd dro drr drt dta dtb dtd dtf dto dtr dtt faa fab fad faf fao far fat fba fbb fbd fbf fbo fbr fbt fda fdb fdd fdf fdo fdr fdt ffa ffd fff ffo ffr fft foa fob fof foo for fot fra frb frd frf fro frr frt fta ftb ftd ftf fto ftr ftt oaa oab oad oaf oao oar oat ob- oba obb obd obf obo obr obt oda odb odd odf odo odr odt of- ofa ofb ofd off ofo ofr oft oo- ooa oob ood oof ooo oor oot or- ora orb ord orf oro orr ort ot- ota otb otd otf oto otr ott ra- raa rab rad raf rao rar rat rba rbb rbd rbf rbo rbr rbt rda rdb rdd rdf rdo rdr rdt rfa rfb rfd rff rfo rfr rft roa rob rod rof roo ror rot rra rrb rrd rrf rrr rrt rta rtb rtd rtf rto rtr rtt taa tab tad taf tao tar tat tba tbb tbd tbf tbo tbr tbt tda tdb tdd tdf tdo tdr tdt tfa tfb tfd tff tfo tfr tft to- toa tob tod tof too tor tot tra trb trd trf tro trr trt tta ttb ttd ttf tto ttr ttt