a-a a-b a-c a-z aaa aab aac aae aan aaz ab- aba abb abc abe abn abz ac- aca acb acc ace acn acz aea aeb aec aee aen aez an- ana anb anc ane ann anz az- aza azb aze azn azz baa bab bac bae ban baz bba bbb bbc bbe bbn bca bcb bcc bce bcn bcz be- bea beb bec bee ben bez bna bnb bnc bne bnn bnz bza bze bzn bzz c-- caa cab cac cae can caz cba cbb cbc cbe cbn cbz cca ccb ccc cce ccn ccz ce- cea ceb cec cee cen cez cn- cna cnb cnc cne cnn cz- czc cze eaa eab eac eae ean eaz eba ebb ebc ebe ebn ec- eca ecb ecc ece ecn eea eeb eec eee een en- ena enb enc ene enn enz eze ezz naa nab nac nae nan naz nba nbb nbc nbe nbn nca ncb ncc nce ncn ne- nea neb nec nee nen nez nna nnb nnc nne nnn nnz nzb nze nzz zaa zab zac zan zaz zbb zbc zce zea zeb zec zee zen zez znc zne znn zzz