-er a-a a-b a-c aaa aab aac aae aao aar aau ab- aba abb abc abe abo abr abu ac- aca acb acc ace aco acr acu aea aeb aec aee aeo aer aeu aoa aob aoc aoe aoo aor aou ar- ara arb arc are aro arr aru au- aua aub auc aue auo aur b-u baa bab bac bae bao bar bau bba bbb bbc bbe bbo bbr bbu bca bcb bcc bce bco bcr bcu be- bea beb bec bee beo ber beu boa bob boc boe boo bor bou bra brb bre bro brr bru bua bub buc bue buo bur buu c-- caa cab cac cae cao car cau cba cbb cbc cbe cbo cbr cbu cca ccb ccc cce cco ccr ccu ce- cea ceb cec cee ceo cer ceu co- coa cob coc coe coo cor cou cra crb crc cre cro crr cru cua cub cuc cue cuo cur cuu eaa eab eac eae eao ear eau eba ebb ebc ebe ebo ebr ebu ec- eca ecb ecc ece eco ecr ecu eea eeb eec eee eeo eer eo- eoa eob eoc eoe eoo eor eou era erb erc ere ero err eru eu- eua eub euc eue eur oaa oab oac oae oao oar oau ob- oba obb obc obe obo obr obu oc- oca ocb occ oco ocr ocu oea oeb oec oee oeo oer oo- ooa oob ooc ooo oor or- ora orb orc ore oro orr oru ou- oua ouc oue ouo our ra- raa rab rac rae rao rar rau rba rbb rbc rbe rbo rbr rbu rca rcb rcc rce rco rcr rcu re- rea reb rec ree reo rer reu roa rob roc roe roo ror rou rra rrb rrc rrr rru rua rub ruc rue ruo rur ruu ua- uaa uab uac uae uao uar uau uba ubb ubc ube ubo ubr ubu uca ucb ucc uce uco ucr ucu uea ueb uec uee uer uoa uob uoc uoe uoo uor ur- ura urb urc ure uro urr uru uua uuc uue uur uuu