a-a a-b a-c aaa aab aac aan aao aar aas aax ab- aba abb abc abn abo abr abs abx ac- aca acb acc acn aco acr acs acx an- ana anb anc ann ano anr ans anx aoa aob aoc aon aoo aor aos aox ar- ara arb arc arn aro arr ars arx as- asa asb asc asn aso asr ass asx ax- axa axn axo axr axs axx baa bab bac ban bao bar bas bax bba bbb bbc bbn bbo bbr bbs bbx bca bcb bcc bcn bco bcr bcs bcx bna bnb bnc bnn bno bnr bns bnx boa bob boc bon boo bor bos box bra brb brn bro brr brs brx bsa bsb bsc bsn bso bsr bss bsx bxb bxn bxo bxx c-- caa cab cac can cao car cas cax cba cbb cbc cbn cbo cbr cbs cbx cca ccb ccc ccn cco ccr ccs ccx cn- cna cnb cnc cnn cno cnr cns cnx co- coa cob coc con coo cor cos cox cra crb crc crn cro crr crs crx csa csb csc csn cso csr css csx cxc cxo cxr cxs cxx naa nab nac nan nao nar nas nax nba nbb nbc nbn nbo nbr nbs nbx nca ncb ncc ncn nco ncr ncs ncx nna nnb nnc nnn nno nns no- noa nob noc non noo nor nos nox nra nrb nrc nrn nro nrr nrs nrx nsa nsb nsc nsn nso nsr nss nsx nxc oaa oab oac oan oao oar oas oax ob- oba obb obc obn obo obr obs obx oc- oca ocb occ ocn oco ocr ocs ocx on- ona onb onc onn ono onr ons onx oo- ooa oob ooc oon ooo oor oos oox or- ora orb orc orn oro orr ors orx os- osa osb osc osn oso osr oss osx ox- oxa oxb oxc oxn oxo oxx ra- raa rab rac ran rao rar ras rax rba rbb rbc rbn rbo rbr rbs rbx rca rcb rcc rcn rco rcr rcs rcx rna rnb rnc rnn rno rnr rns roa rob roc ron roo ror ros rox rra rrb rrc rrn rrr rrs rsa rsb rsc rsn rso rsr rss rsx rxr rxs saa sab sac san sao sar sas sax sba sbb sbc sbn sbo sbr sbs sbx sca scb scc scn sco scr scs scx sna snb snc snn sno snr sns soa sob soc son soo sor sos sox sr- sra srb src srn sro srr srs srx ss- ssa ssb ssc ssn sso ssr sss ssx sxc sxn sxs xaa xac xan xar xas xbc xbr xbx xcb xcr xcx xna xnc xno xns xoa xoc xon xoo xor xos xox xrc xrx xsa xsb xsc xss xxo xxx