-er a-a a-b aaa aab aae aag aak aan aar ab- aba abb abe abg abk abn abr aea aeb aee aeg aek aen aer ag- aga agb age agg agk agn agr aka akb ake akg akk akn akr an- ana anb ane ang ank ann anr ar- ara arb are arg ark arn arr baa bab bae bag bak ban bar bba bbb bbe bbg bbk bbn bbr be- bea beb bee beg bek ben ber bga bgb bge bgg bgk bgn bgr bka bkb bke bkg bkk bkn bkr bna bnb bne bng bnk bnn bnr bra brb bre brg brk brn brr eaa eab eae eag eak ean ear eba ebb ebe ebg ebk ebn ebr eea eeb eee eeg eek een eer ega egb ege egg egn egr eka ekb eke ekg ekr en- ena enb ene eng enk enn enr era erb ere erg erk ern err gaa gab gae gag gak gan gar gba gbe gbg gbk gbn gbr ge- gea geb gee geg gek gen ger gga ggb ggg ggn ggr gka gkb gkn gna gnb gne gnn gnr gra grb gre grg grk grn grr ka- kaa kab kae kag kak kan kar kba kbb kbe kbk kbn kbr ke- kea keb kee keg kek ken ker kga kgb kkb kke kkk kkn kkr kn- kna kne kng knk knn knr kra krg krk krn krr naa nab nae nag nak nan nar nba nbb nbe nbg nbk nbn nbr ne- nea neb nee neg nek nen ner nga ngb nge ngg ngk ngn nka nke nkk nkn nkr nna nnb nne nng nnk nnn nra nrb nre nrg nrk nrn nrr ra- raa rab rae rag rak ran rar rba rbb rbe rbg rbk rbn rbr re- rea reb ree reg rek ren rer rga rgb rge rgg rgk rgn rgr rkb rke rkg rkk rna rnb rng rnn rnr rra rrb rrg rrk rrn rrr