a-a a-b aaa aab aao aar aaw ab- aba abb abo abr abw aoa aob aoo aor aow ar- ara arb aro arr arw aw- awa awb awo awr aww baa bab bao bar baw bba bbb bbo bbr bbw boa bob boo bor bow bra brb bro brr brw bwa bwb bwo bwr oaa oab oao oar oaw ob- oba obb obo obr obw oo- ooa oob ooo oor oow or- ora orb oro orr owa owb owo oww ra- raa rab rao rar raw rba rbb rbo rbr rbw roa rob roo ror row rra rrb rrr rwa rwb rwr waa wab wao war waw wba wbb wbo wbr wbw woa wob woo wor wow wr- wra wro wrr wrw wwa wwo www