a-a a-b a-c aaa aab aac aao aar aax ab- aba abb abc abo abr abx ac- aca acb acc aco acr acx aoa aob aoc aoo aor aox ar- ara arb arc aro arr arx ax- axa axo axr axx baa bab bac bao bar bax bba bbb bbc bbo bbr bbx bca bcb bcc bco bcr bcx boa bob boc boo bor box bra brb bro brr brx bxb bxo bxx c-- caa cab cac cao car cax cba cbb cbc cbo cbr cbx cca ccb ccc cco ccr ccx co- coa cob coc coo cor cox cra crb crc cro crr crx cxc cxo cxr cxx oaa oab oac oao oar oax ob- oba obb obc obo obr obx oc- oca ocb occ oco ocr ocx oo- ooa oob ooc ooo oor oox or- ora orb orc oro orr orx ox- oxa oxb oxc oxo oxx ra- raa rab rac rao rar rax rba rbb rbc rbo rbr rbx rca rcb rcc rco rcr rcx roa rob roc roo ror rox rra rrb rrc rrr rxr xaa xac xar xbc xbr xbx xcb xcr xcx xoa xoc xoo xor xox xrc xrx xxo xxx