a-a a-b aaa aab aaf aak aan aar ab- aba abb abf abk abn abr af- afa afb aff afk afn afr aka akb akk akn akr an- ana anb anf ank ann anr ar- ara arb arf ark arn arr baa bab baf bak ban bar bba bbb bbf bbk bbn bbr bfa bfb bff bfn bfr bka bkb bkf bkk bkn bkr bna bnb bnf bnk bnn bnr bra brb brf brk brn brr faa fab faf fak fan far fba fbb fbf fbk fbn fbr ffa fff ffk ffn ffr fka fkb fkf fkk fna fnb fnf fnk fnn fnr fra frb frf frk frn frr ka- kaa kab kaf kak kan kar kba kbb kbf kbk kbn kbr kfa kff kkb kkk kkn kkr kn- kna knf knk knn knr kra krf krk krn krr naa nab naf nak nan nar nba nbb nbf nbk nbn nbr nfa nfb nff nfk nfn nfr nka nkf nkk nkn nkr nna nnb nnf nnk nnn nra nrb nrf nrk nrn nrr ra- raa rab raf rak ran rar rba rbb rbf rbk rbn rbr rfa rfb rff rfk rfn rfr rkb rkf rkk rna rnb rnn rnr rra rrb rrf rrk rrn rrr