a-a a-b a-c aaa aab aac aan aau ab- aba abb abc abn abu ac- aca acb acc acn acu an- ana anb anc ann anu au- aua aub auc aun b-u baa bab bac ban bau bba bbb bbc bbn bbu bca bcb bcc bcn bcu bna bnb bnc bnn bnu bua bub buc bun buu c-- caa cab cac can cau cba cbb cbc cbn cbu cca ccb ccc ccn ccu cn- cna cnb cnc cnn cnu cua cub cuc cun cuu naa nab nac nan nau nba nbb nbc nbn nbu nca ncb ncc ncn ncu nna nnb nnc nnn nnu nua nub nuc nun nuu ua- uaa uab uac uan uau uba ubb ubc ubn ubu uca ucb ucc ucn ucu un- una unb unc unn unu uua uuc uun uuu