-er a-a a-b a-c aaa aab aac aae aag aak aan aar ab- aba abb abc abe abg abk abn abr ac- aca acb acc ace acg ack acn acr aea aeb aec aee aeg aek aen aer ag- aga agb agc age agg agk agn agr aka akb akc ake akg akk akn akr an- ana anb anc ane ang ank ann anr ar- ara arb arc are arg ark arn arr baa bab bac bae bag bak ban bar bba bbb bbc bbe bbg bbk bbn bbr bca bcb bcc bce bcg bck bcn bcr be- bea beb bec bee beg bek ben ber bga bgb bgc bge bgg bgk bgn bgr bka bkb bkc bke bkg bkk bkn bkr bna bnb bnc bne bng bnk bnn bnr bra brb bre brg brk brn brr c-- caa cab cac cae cag cak can car cba cbb cbc cbe cbg cbk cbn cbr cca ccb ccc cce ccg cck ccn ccr ce- cea ceb cec cee ceg cek cen cer cga cgb cgc cge cgg cgn cgr cka ckb ckc cn- cna cnb cnc cne cng cnn cnr cra crb crc cre crg crk crn crr eaa eab eac eae eag eak ean ear eba ebb ebc ebe ebg ebk ebn ebr ec- eca ecb ecc ece ecg eck ecn ecr eea eeb eec eee eeg eek een eer ega egb egc ege egg egn egr eka ekb ekc eke ekg ekr en- ena enb enc ene eng enk enn enr era erb erc ere erg erk ern err gaa gab gac gae gag gak gan gar gba gbc gbe gbg gbk gbn gbr gca gcb gcc gce gcg gck gcn gcr ge- gea geb gec gee geg gek gen ger gga ggb ggc ggg ggn ggr gka gkb gkn gna gnb gnc gne gnn gnr gra grb grc gre grg grk grn grr ka- kaa kab kac kae kag kak kan kar kba kbb kbc kbe kbk kbn kbr kca kcb kcc kce kcg kck kcn kcr ke- kea keb kec kee keg kek ken ker kga kgb kgc kkb kkc kke kkk kkn kkr kn- kna knc kne kng knk knn knr kra krc krg krk krn krr naa nab nac nae nag nak nan nar nba nbb nbc nbe nbg nbk nbn nbr nca ncb ncc nce ncg nck ncn ncr ne- nea neb nec nee neg nek nen ner nga ngb ngc nge ngg ngk ngn nka nkc nke nkk nkn nkr nna nnb nnc nne nng nnk nnn nra nrb nrc nre nrg nrk nrn nrr ra- raa rab rac rae rag rak ran rar rba rbb rbc rbe rbg rbk rbn rbr rca rcb rcc rce rcg rcn rcr re- rea reb rec ree reg rek ren rer rga rgb rgc rge rgg rgk rgn rgr rkb rkc rke rkg rkk rna rnb rnc rng rnn rnr rra rrb rrc rrg rrk rrn rrr