a-a a-b a-c aaa aab aac aad aao aar ab- aba abb abc abd abo abr ac- aca acb acc acd aco acr ad- ada adb adc add ado adr aoa aob aoc aod aoo aor ar- ara arb arc ard aro arr baa bab bac bad bao bar bba bbb bbc bbd bbo bbr bca bcb bcc bcd bco bcr bda bdb bdc bdd bdo bdr boa bob boc bod boo bor bra brb brd bro brr c-- caa cab cac cad cao car cba cbb cbc cbd cbo cbr cca ccb ccc ccd cco ccr cda cdb cdc cdd cdo cdr co- coa cob coc cod coo cor cra crb crc crd cro crr daa dab dac dad dao dar dba dbb dbc dbd dbo dbr dca dcb dcc dcd dco dcr dda ddb ddc ddd ddo ddr doa dob doc dod doo dor dra drb drc drd dro drr oaa oab oac oad oao oar ob- oba obb obc obd obo obr oc- oca ocb occ ocd oco ocr oda odb odc odd odo odr oo- ooa oob ooc ood ooo oor or- ora orb orc ord oro orr ra- raa rab rac rad rao rar rba rbb rbc rbd rbo rbr rca rcb rcc rcd rco rcr rda rdb rdc rdd rdo rdr roa rob roc rod roo ror rra rrb rrc rrd rrr