-er a-a a-b a-c aaa aab aac aad aae aao aar ab- aba abb abc abd abe abo abr ac- aca acb acc acd ace aco acr ad- ada adb adc add ade ado adr aea aeb aec aed aee aeo aer aoa aob aoc aod aoe aoo aor ar- ara arb arc ard are aro arr baa bab bac bad bae bao bar bba bbb bbc bbd bbe bbo bbr bca bcb bcc bcd bce bco bcr bda bdb bdc bdd bde bdo bdr be- bea beb bec bed bee beo ber boa bob boc bod boe boo bor bra brb brd bre bro brr c-- caa cab cac cad cae cao car cba cbb cbc cbd cbe cbo cbr cca ccb ccc ccd cce cco ccr cda cdb cdc cdd cde cdo cdr ce- cea ceb cec ced cee ceo cer co- coa cob coc cod coe coo cor cra crb crc crd cre cro crr daa dab dac dad dae dao dar dba dbb dbc dbd dbe dbo dbr dca dcb dcc dcd dce dco dcr dda ddb ddc ddd dde ddo ddr de- dea deb dec ded dee deo der doa dob doc dod doe doo dor dra drb drc drd dre dro drr eaa eab eac ead eae eao ear eba ebb ebc ebd ebe ebo ebr ec- eca ecb ecc ecd ece eco ecr ed- eda edb edc edd ede edo edr eea eeb eec eed eee eeo eer eo- eoa eob eoc eod eoe eoo eor era erb erc erd ere ero err oaa oab oac oad oae oao oar ob- oba obb obc obd obe obo obr oc- oca ocb occ ocd oco ocr oda odb odc odd ode odo odr oea oeb oec oed oee oeo oer oo- ooa oob ooc ood ooo oor or- ora orb orc ord ore oro orr ra- raa rab rac rad rae rao rar rba rbb rbc rbd rbe rbo rbr rca rcb rcc rcd rce rco rcr rda rdb rdc rdd rde rdo rdr re- rea reb rec red ree reo rer roa rob roc rod roe roo ror rra rrb rrc rrd rrr