a-ak a-do a-ok aaaa aaab aaad aaba aabb aabd aada aaka aaoo abaa abab abad abak abb- abba abbb abbo abda abdo aboa abob abod abok aboo adaa adab adad adak adao adba adda addd addo adob adod adok adoo akaa akao akka akko akok aoba baaa baad baak baba babb babo bada badb badd bado bak- baka bako bbad bbbb bbdd bbdo boab boad boak boba bobb bobo boda bodb bodo boka boko boob bood book d-bo daab daad daba dabb dabo dada dado daka dako dddd dkba doab doak doba dobb dod- doda dodd dodo doka doko doob dood dook kaaa kaab kaak kaba kabb kabd kabo kad- kada kadd kado kaka kakk kako kaoa kaok kbaa kbab kbad kbak kbba kbbb kbbd kbbk kbbo kbdb kbdo kbkb kbkk kbko kboa kbob kbod kbok kboo kdaa kdab kdad kdak kdao kdbb kddb kddd kddk kdka kdkb kdkd kdkk kdko kdok kkaa kkba kkbb kkbd kkbo kkda kkdd kkdo kkkk kkoa kkob kkoo koab koak koba kobb kobk kobo koda kodk kodo koka kokb kokk koko koob kook kooo obad obak obba obbo obkb obok odbo odda oddd odoo okak okka okko okok ooaa ooak ooba ooda oooo