a-a a-b a-c a-z aaa aab aac aae aaz ab- aba abb abc abe abz ac- aca acb acc ace acz aea aeb aec aee aez az- aza azb aze azz baa bab bac bae baz bba bbb bbc bbe bca bcb bcc bce bcz be- bea beb bec bee bez bza bze bzz c-- caa cab cac cae caz cba cbb cbc cbe cbz cca ccb ccc cce ccz ce- cea ceb cec cee cez cz- czc cze eaa eab eac eae eaz eba ebb ebc ebe ec- eca ecb ecc ece eea eeb eec eee eze ezz zaa zab zac zaz zbb zbc zce zea zeb zec zee zez zzz