a-ak a-ok aaaa aaab aaav aaba aabb aaka aaoo aava abaa abab abak abb- abba abbb abbo aboa abob abok aboo abov abva akaa akao akka akko akok aoba avab avao avva avvo baaa baak baba babb babo bak- baka bako bava bbbb boab boak boba bobb bobo boka boko boob book bova bovo kaaa kaab kaak kaba kabb kabo kaka kakk kako kaoa kaok kava kavb kavo kavv kbaa kbab kbak kbba kbbb kbbk kbbo kbkb kbkk kbko kbkv kboa kbob kbok kboo kbov kbva kbvb kbvo kkaa kkba kkbb kkbo kkkk kkoa kkob kkoo kkov kkvv koab koak koba kobb kobk kobo koka kokb kokk koko koob kook kooo koov kova kovk kovo kvab kvak kvoa kvob kvok kvoo kvov kvvv obak obba obbo obkb obok okak okka okko okok ooaa ooak ooba oooo ovo- ovoo vaka vava voka vovk vvob vvvv