a-a a-b a-c aaa aab aac aag aao aar ab- aba abb abc abg abo abr ac- aca acb acc acg aco acr ag- aga agb agc agg ago agr aoa aob aoc aog aoo aor ar- ara arb arc arg aro arr baa bab bac bag bao bar bba bbb bbc bbg bbo bbr bca bcb bcc bcg bco bcr bga bgb bgc bgg bgo bgr boa bob boc bog boo bor bra brb brg bro brr c-- caa cab cac cag cao car cba cbb cbc cbg cbo cbr cca ccb ccc ccg cco ccr cga cgb cgc cgg cgo cgr co- coa cob coc cog coo cor cra crb crc crg cro crr gaa gab gac gag gao gar gba gbc gbg gbo gbr gca gcb gcc gcg gco gcr gga ggb ggc ggg ggo ggr goa gob goc gog goo gor gra grb grc grg gro grr oaa oab oac oag oao oar ob- oba obb obc obg obo obr oc- oca ocb occ ocg oco ocr oga ogc ogg ogo oo- ooa oob ooc oog ooo oor or- ora orb orc org oro orr ra- raa rab rac rag rao rar rba rbb rbc rbg rbo rbr rca rcb rcc rcg rco rcr rga rgb rgc rgg rgo rgr roa rob roc rog roo ror rra rrb rrc rrg rrr