a-a a-b a-c aaa aab aac aao aar aax aay ab- aba abb abc abo abr abx aby ac- aca acb acc aco acr acx acy aoa aob aoc aoo aor aox ar- ara arb arc aro arr arx ary ax- axa axo axr axx ay- aya ayc ayo ayr ayx baa bab bac bao bar bax bay bba bbb bbc bbo bbr bbx bby bca bcb bcc bco bcr bcx bcy boa bob boc boo bor box boy bra brb bro brr brx bry bxb bxo bxx by- bya byc byo byr c-- caa cab cac cao car cax cay cba cbb cbc cbo cbr cbx cby cca ccb ccc cco ccr ccx co- coa cob coc coo cor cox coy cra crb crc cro crr crx cry cxc cxo cxr cxx cya cyb cyc cyo cyr oaa oab oac oao oar oax ob- oba obb obc obo obr obx oby oc- oca ocb occ oco ocr ocx oo- ooa oob ooc ooo oor oox or- ora orb orc oro orr orx ory ox- oxa oxb oxc oxo oxx oxy oya oyo ra- raa rab rac rao rar rax ray rba rbb rbc rbo rbr rbx rca rcb rcc rco rcr rcx roa rob roc roo ror rox roy rra rrb rrc rrr rxr ry- rya ryc ryo ryr ryy xaa xac xar xbc xbr xbx xcb xcr xcx xoa xoc xoo xor xox xrc xrx xry xxo xxx xxy xyr xyy yaa yab yac yao yar yax yay ybc ybr yby yca ycc yco ycy yob yoc yoo yor yox yoy yra yrc yro yxa yxy yyb yyc yyy