a-a a-b a-c aaa aab aac aag aan aao aar ab- aba abb abc abg abn abo abr ac- aca acb acc acg acn aco acr ag- aga agb agc agg agn ago agr an- ana anb anc ang ann ano anr aoa aob aoc aog aon aoo aor ar- ara arb arc arg arn aro arr baa bab bac bag ban bao bar bba bbb bbc bbg bbn bbo bbr bca bcb bcc bcg bcn bco bcr bga bgb bgc bgg bgn bgo bgr bna bnb bnc bng bnn bno bnr boa bob boc bog bon boo bor bra brb brg brn bro brr c-- caa cab cac cag can cao car cba cbb cbc cbg cbn cbo cbr cca ccb ccc ccg ccn cco ccr cga cgb cgc cgg cgn cgo cgr cn- cna cnb cnc cng cnn cno cnr co- coa cob coc cog con coo cor cra crb crc crg crn cro crr gaa gab gac gag gan gao gar gba gbc gbg gbn gbo gbr gca gcb gcc gcg gcn gco gcr gga ggb ggc ggg ggn ggo ggr gna gnb gnc gnn gno gnr goa gob goc gog gon goo gor gra grb grc grg grn gro grr naa nab nac nag nan nao nar nba nbb nbc nbg nbn nbo nbr nca ncb ncc ncg ncn nco ncr nga ngb ngc ngg ngn ngo nna nnb nnc nng nnn nno no- noa nob noc nog non noo nor nra nrb nrc nrg nrn nro nrr oaa oab oac oag oan oao oar ob- oba obb obc obg obn obo obr oc- oca ocb occ ocg ocn oco ocr oga ogc ogg ogn ogo on- ona onb onc ong onn ono onr oo- ooa oob ooc oog oon ooo oor or- ora orb orc org orn oro orr ra- raa rab rac rag ran rao rar rba rbb rbc rbg rbn rbo rbr rca rcb rcc rcg rcn rco rcr rga rgb rgc rgg rgn rgo rgr rna rnb rnc rng rnn rno rnr roa rob roc rog ron roo ror rra rrb rrc rrg rrn rrr