-er a-a a-b a-c a-t aaa aab aac aae aao aar aat ab- aba abb abc abe abo abr abt ac- aca acb acc ace aco acr act aea aeb aec aee aeo aer aet aoa aob aoc aoe aoo aor aot ar- ara arb arc are aro arr art at- ata atb atc ate ato atr att baa bab bac bae bao bar bat bba bbb bbc bbe bbo bbr bbt bca bcb bcc bce bco bcr bct be- bea beb bec bee beo ber bet boa bob boc boe boo bor bot bra brb bre bro brr brt bta btb btc bte bto btr btt c-- caa cab cac cae cao car cat cba cbb cbc cbe cbo cbr cbt cca ccb ccc cce cco ccr cct ce- cea ceb cec cee ceo cer cet co- coa cob coc coe coo cor cot cra crb crc cre cro crr crt cta ctb ctc cte cto ctr ctt eaa eab eac eae eao ear eat eba ebb ebc ebe ebo ebr ebt ec- eca ecb ecc ece eco ecr ect eea eeb eec eee eeo eer eet eo- eoa eob eoc eoe eoo eor eot era erb erc ere ero err ert eta etb etc ete eto etr ett oaa oab oac oae oao oar oat ob- oba obb obc obe obo obr obt oc- oca ocb occ oco ocr oct oea oeb oec oee oeo oer oet oo- ooa oob ooc ooo oor oot or- ora orb orc ore oro orr ort ot- ota otb otc ote oto otr ott ra- raa rab rac rae rao rar rat rba rbb rbc rbe rbo rbr rbt rca rcb rcc rce rco rcr rct re- rea reb rec ree reo rer ret roa rob roc roe roo ror rot rra rrb rrc rrr rrt rta rtb rtc rte rto rtr rtt taa tab tac tae tao tar tat tba tbb tbc tbe tbo tbr tbt tca tcb tcc tce tco tcr tct te- tea teb tec tee teo ter tet to- toa tob toc toe too tor tot tra trb trc tre tro trr trt tta ttb ttc tte tto ttr ttt