a-ak aaaa aaab aaac aaar aaba aabb aabc aaca aacb aacc aack aacr aaka aara aarc abaa abab abac abak abar abb- abba abbb abbr abca abcb abcc abcr abra abrc acaa acab acac acar acba acca accc acr- acra acrc acrr akaa akar akca akka akr- akra arab arac arak arar arba arc- arca arka arr- arra arrc arrk arrr baaa baak baar baba babb babr bac- baca bacc back bak- baka bakr bar- bara barb barc bark barr bbbb bbrc bcaa bcar bcbc bcca bccc bcra brab brac brak brca brcb brka brkb brrr caaa caab caac caba cac- caca cacc cack cacr caka cara carb carc cark carr cbac cbar cbbc cbca cbcc cbcr cbka cbkr ccaa ccab ccac ccar ccba ccbc ccca cccb cccc ccra ccrc ckac ckbc ckck ckrc crab crac crar crbc crca crcc crcr crkc kaaa kaab kaak kaar kaba kabb kabc kabr kacb kacc kaka kakc kakk kara karb kark karr kbaa kbab kbac kbak kbar kbba kbbb kbbc kbbk kbbr kbca kbcb kbck kbcr kbkb kbkk kbkr kbra kbrb kbrc kbrk kcaa kcab kcac kcar kcba kcbc kcbk kcbr kcca kccb kccc kcck kccr kckc kckk kckr kcrc kcrr kkaa kkac kkar kkba kkbb kkbr kkcb kkck kkcr kkkk kkrb kkrc kkrk kkrr krab krac krak krar krba krbb krbk krbr krca krcb krcc krka krkc krkk krkr krrb krrc krrk krrr raab raak raba rabb rabk rac- raca racc rack raka rakk rara rarb rark rbbb rbbr rcac rcbc rccb rccc rrrr