a-a a-b a-c aaa aab aac aae aak aao aas aax ab- aba abb abc abe abk abo abs abx ac- aca acb acc ace ack aco acs acx aea aeb aec aee aek aeo aes aex aka akb akc ake akk ako aks aoa aob aoc aoe aok aoo aos aox as- asa asb asc ase ask aso ass asx ax- axa axe axk axo axs axx baa bab bac bae bak bao bas bax bba bbb bbc bbe bbk bbo bbs bbx bca bcb bcc bce bck bco bcs bcx be- bea beb bec bee bek beo bes bex bka bkb bkc bke bkk bko bks bkx boa bob boc boe bok boo bos box bsa bsb bsc bse bsk bso bss bsx bxb bxo bxx c-- caa cab cac cae cak cao cas cax cba cbb cbc cbe cbk cbo cbs cbx cca ccb ccc cce cck cco ccs ccx ce- cea ceb cec cee cek ceo ces cex cka ckb ckc cko cks ckx co- coa cob coc coe cok coo cos cox csa csb csc cse csk cso css csx cxc cxk cxo cxs cxx eaa eab eac eae eak eao eas eax eba ebb ebc ebe ebk ebo ebs ebx ec- eca ecb ecc ece eck eco ecs ecx eea eeb eec eee eek eeo ees eex eka ekb ekc eke eko eks eo- eoa eob eoc eoe eok eoo eos es- esa esb esc ese esk eso ess esx ex- exa exc exe exo exs exx ka- kaa kab kac kae kak kao kas kax kba kbb kbc kbe kbk kbo kbs kbx kca kcb kcc kce kck kcs kcx ke- kea keb kec kee kek keo kes kex kkb kkc kke kkk kks koa kob koc koe kok koo kos ksa ksb ksc kse ksk kso kss kxo oaa oab oac oae oak oao oas oax ob- oba obb obc obe obk obo obs obx oc- oca ocb occ ock oco ocs ocx oea oeb oec oee oeo oes oex oka okb okc oke okk oko oks oo- ooa oob ooc ook ooo oos oox os- osa osb osc ose osk oso oss osx ox- oxa oxb oxc oxo oxx saa sab sac sae sak sao sas sax sba sbb sbc sbe sbk sbo sbs sbx sca scb scc sce sck sco scs scx se- sea seb sec see sek seo ses sex sk- ska skb skc ske skk sko sks skx soa sob soc soe sok soo sos sox ss- ssa ssb ssc sse ssk sso sss ssx sxc sxs xaa xac xak xas xbc xbe xbx xcb xcx xee xes xex xkb xke xks xoa xoc xok xoo xos xox xsa xsb xsc xss xxo xxx