aaaa aaab aaaf aaap aaar aaba aabb aabp aafa aafb aaff aaoo aapa aapo aara aaro aarp abaa abab abaf abap abar abb- abba abbb abbo abbr abff aboa abob abof aboo abor abpa abpp abpr abra abro afaa afao afap afar affa affo afoa afoo afor afpa afr- afra afro aoba aopo aora aorb apao apap apar apba apbr apfa apfo apo- apof apoo apop apor appa appr apra apro arab araf arap arar arba arfa arfb arff aroa arob aroo aror arpa arr- arra arro arrr baaa baaf baar baba babb babo babr baff bafo bapa bapp bar- bara barb barf baro barr bbbb bbpr bfpo bfpp boab boar boba bobb bobo bofa boff boob boof boop boor bopa bopp bor- bora borf boro borr brab braf brao broa brob broo bror brrr faaa faap faba fabo fafa faff fafo fapa fapp fara farb faro farp farr fbar fbop ffar ffff ffrr foaf foar foba fofo foof fopp for- fora forb foro forr fpaa fpra fprf frab frap frob frop oafo oara obba obbo obor obra obro off- offa offo offr ofor ofra ooaa ooba ooff oooo oora opap opar opo- opor oppa oppo opra orab orao orar orba orbb orbo orff oro- orof oror orra orro paap paar paba pafa paff papa papb papp papr par- para parf paro parp parr pbar pbpa pbrf pfaa pfff pffr pfra poar poba pobo poff poof poop poor pop- popa popo popp pora porb poro porr ppap ppar ppfa ppoa pppa pppo pppp pprf prao prar pro- proa prob prof proo prop raab raaf raba rabb rabo rafa raff raob raop rapa rapp rara rarb rarf raro rbaf rbbb rbbr roab roaf roap roar rob- roba robb robo roff rofo roob roof roop roor ropa ropo rora roro rpob rpof rrrr