a-a a-b a-c a-z aaa aab aac aar aaz ab- aba abb abc abr abz ac- aca acb acc acr acz ar- ara arb arc arr arz az- aza azb azz baa bab bac bar baz bba bbb bbc bbr bca bcb bcc bcr bcz bra brb brr brz bza bzr bzz c-- caa cab cac car caz cba cbb cbc cbr cbz cca ccb ccc ccr ccz cra crb crc crr crz cz- czc ra- raa rab rac rar raz rba rbb rbc rbr rca rcb rcc rcr rra rrb rrc rrr rza rzb zaa zab zac zar zaz zbb zbc zbr zzr zzz