a-ak aaaa aaab aaac aaaf aaba aabb aabc aaca aacb aacc aacf aack aafa aafb aafc aaff aaka abaa abab abac abaf abak abax abb- abba abbb abca abcb abcc abcf abff acaa acab acac acba acca accc accf acfc afaa afak afca afcb afcc affa affc afka akaa akca akka axaf ba-x baaa baaf baak baba babb bac- baca bacc back bafc baff bak- baka bbbb bbfc bcaa bcbc bcca bccc bcfc bfca caaa caab caac caaf caba cabf cac- caca cacc cack cafa cafb cafc caff caka caxa cbac cbax cbbc cbca cbcc cbfb cbfc cbka cbxa ccaa ccab ccac ccaf ccba ccbc ccca cccb cccc cccf ccfa ccfc ccff cfaa cfab cfac cfax cfbc cfca cfcb cfcf cffb ckac ckbc ckbx ckck ckcx cxxx f--k faaa faac faba faca facc fack fafa fafc faff fcab fcba fcca fccf ffcc ffff fkab kaaa kaab kaaf kaak kaba kabb kabc kabf kacb kacc kafa kafc kaff kaka kakc kakk kakx kaxa kbaa kbab kbac kbak kbba kbbb kbbc kbbf kbbk kbca kbcb kbck kbfb kbfc kbff kbfk kbfx kbkb kbkf kbkk kbxb kbxx kc-x kcaa kcab kcac kcba kcbc kcbf kcbk kcbx kcca kccb kccc kcck kcfa kcfb kcfc kcfx kckc kckf kckk kckx kfab kfac kfax kfbc kfbk kfbx kfcf kffa kffb kfff kffk kffx kfka kfkb kfkx kfxa kfxf kfxx kkaa kkac kkba kkbb kkcb kkck kkkk kkxa kkxk kkxx kxaa kxac kxba kxbx kxca kxfc kxff kxkc kxkk kxkx kxxf kxxk kxxx xxxx