a-ak a-do a-ok aaaa aaab aaac aaad aaba aabb aabc aabd aaca aacb aacc aacd aack aaco aada aadc aaka aaoo abaa abab abac abad abak abb- abba abbb abbo abca abcb abcc abcd abda abdo aboa abob abod abok aboo acaa acab acac acad acba acca accc accd acco acda acdb acdc ackd acoa acod adaa adab adac adad adak adao adba adbc adcc adda addc addd addo adob adoc adod adok adoo akaa akao akca akka akko akok aoba aoca baaa baad baak baba babb babo bac- baca bacc back baco bada badb badd bado bak- baka bako bbad bbbb bbdd bbdo bcaa bcbc bcca bccc bcda bdbc bddc boab boac boad boak boba bobb bobo boca bock boco boda bodb bodo boka boko boob booc bood book c-bo c-cd caaa caab caac caba cabo cac- caca cacc cack caco cada cadc cadd cado caka caod cbac cbbc cbca cbcc cbdb cbdc cbdo cbka cbko ccaa ccab ccac ccad ccba ccbc ccca cccb cccc ccdc ccob ccoc ccod cdaa cdac cdad cdba cdda cddb ckac ckbc ckck ckco ckdo ckoa ckob ckoc ckoo coad coak coba cobb cobo coca cock coco coda codd cok- coka coko coob cood cook d-bo daab daad daba dabb dabo daca dada dado daka dako dbcc dcbc dcca dccb dccc dcdb dddd ddoc dkba dkdc doab doak doba dobb doca dock doco dod- doda dodd dodo doka doko doob dood dook kaaa kaab kaak kaba kabb kabc kabd kabo kacb kacc kacd kaco kad- kada kadd kado kaka kakc kakk kako kaoa kaoc kaok kbaa kbab kbac kbad kbak kbba kbbb kbbc kbbd kbbk kbbo kbca kbcb kbck kbco kbdb kbdo kbkb kbkk kbko kboa kbob kboc kbod kbok kboo kcaa kcab kcac kcad kcba kcbc kcbd kcbk kcca kccb kccc kccd kcck kcda kcdc kcdd kckc kckk kcko kcob kdaa kdab kdac kdad kdak kdao kdbb kdca kdcc kdcd kdco kddb kddc kddd kddk kdka kdkb kdkd kdkk kdko kdoc kdok kkaa kkac kkba kkbb kkbd kkbo kkcb kkcd kkck kkco kkda kkdc kkdd kkdo kkkk kkoa kkob kkoo koab koac koak koba kobb kobc kobk kobo koca kocb kocd kock koda kodk kodo koka kokb kokc kokk koko koob kooc kook kooo obad obak obba obbo obkb obok ocab ocac ocad ocak ocbc occa occc odac odbo odda oddd odoo okak okka okko okok ooaa ooak ooba ooda oooo