-er a-a a-b a-c aaa aab aac aad aae aak aar aau ab- aba abb abc abd abe abk abr abu ac- aca acb acc acd ace ack acr acu ad- ada adb adc add ade adk adr adu aea aeb aec aed aee aek aer aeu aka akb akc akd ake akk akr aku ar- ara arb arc ard are ark arr aru au- aua aub auc aud aue auk aur b-u baa bab bac bad bae bak bar bau bba bbb bbc bbd bbe bbk bbr bbu bca bcb bcc bcd bce bck bcr bcu bda bdb bdc bdd bde bdk bdr bdu be- bea beb bec bed bee bek ber beu bka bkb bkc bke bkk bkr bra brb brd bre brk brr bru bua bub buc bud bue buk bur buu c-- caa cab cac cad cae cak car cau cba cbb cbc cbd cbe cbk cbr cbu cca ccb ccc ccd cce cck ccr ccu cda cdb cdc cdd cde cdk cdr cdu ce- cea ceb cec ced cee cek cer ceu cka ckb ckc ckd cra crb crc crd cre crk crr cru cua cub cuc cud cue cuk cur cuu daa dab dac dad dae dak dar dau dba dbb dbc dbd dbe dbk dbr dbu dca dcb dcc dcd dce dck dcr dcu dda ddb ddc ddd dde ddk ddr ddu de- dea deb dec ded dee dek der deu dka dkb dkc dke dkk dkr dku dra drb drc drd dre drk drr dru dua dub duc dud due duk dur eaa eab eac ead eae eak ear eau eba ebb ebc ebd ebe ebk ebr ebu ec- eca ecb ecc ecd ece eck ecr ecu ed- eda edb edc edd ede edk edr edu eea eeb eec eed eee eek eer eka ekb ekc ekd eke ekr eku era erb erc erd ere erk err eru eu- eua eub euc eud eue eur ka- kaa kab kac kad kae kak kar kau kba kbb kbc kbd kbe kbk kbr kbu kca kcb kcc kcd kce kck kcr kcu kda kdb kdc kde kdk kdr kdu ke- kea keb kec ked kee kek ker kkb kkc kke kkk kkr kku kra krc krd krk krr kru kub kuc kud kue kuk kur kuu ra- raa rab rac rad rae rak rar rau rba rbb rbc rbd rbe rbk rbr rbu rca rcb rcc rcd rce rcr rcu rda rdb rdc rdd rde rdr rdu re- rea reb rec red ree rek rer reu rkb rkc rke rkk rku rra rrb rrc rrd rrk rrr rru rua rub ruc rud rue ruk rur ruu ua- uaa uab uac uad uae uak uar uau uba ubb ubc ube ubk ubr ubu uca ucb ucc ucd uce uck ucr ucu uda udb udc udd ude udk udr udu uea ueb uec ued uee uer uka ukb ukc uke ukk ukr uku ur- ura urb urc urd ure urk urr uru uua uuc uue uur uuu