a-a a-b a-c aaa aab aac aae aak aao aap aax ab- aba abb abc abe abk abo abp abx ac- aca acb acc ace ack aco acp acx aea aeb aec aee aek aeo aep aex aka akb akc ake akk ako akp aoa aob aoc aoe aok aoo aop aox ap- apa apb apc ape apk apo app apx ax- axa axe axk axo axp axx b-p baa bab bac bae bak bao bap bax bba bbb bbc bbe bbk bbo bbp bbx bca bcb bcc bce bck bco bcp bcx be- bea beb bec bee bek beo bep bex bka bkb bkc bke bkk bko bkp bkx boa bob boc boe bok boo bop box bpa bpb bpc bpe bpo bpp bpx bxb bxo bxx c-- caa cab cac cae cak cao cap cax cba cbb cbc cbe cbk cbo cbp cbx cca ccb ccc cce cck cco ccp ccx ce- cea ceb cec cee cek ceo cep cex cka ckb ckc cko ckx co- coa cob coc coe cok coo cop cox cpa cpb cpc cpe cpk cpo cpp cpx cxc cxk cxo cxp cxx eaa eab eac eae eak eao eap eax eba ebb ebc ebe ebk ebo ebp ebx ec- eca ecb ecc ece eck eco ecx eea eeb eec eee eek eeo eep eex eka ekb ekc eke eko ekp eo- eoa eob eoc eoe eok eoo eop ep- epa epb epc epe epo epp epx ex- exa exc exe exo exp exx ka- kaa kab kac kae kak kao kap kax kba kbb kbc kbe kbk kbo kbp kbx kca kcb kcc kce kck kcp kcx ke- kea keb kec kee kek keo kep kex kkb kkc kke kkk kkp koa kob koc koe kok koo kop kpa kpc kpe kpk kpo kpp kxo oaa oab oac oae oak oao oap oax ob- oba obb obc obe obk obo obp obx oc- oca ocb occ ock oco ocp ocx oea oeb oec oee oeo oep oex oka okb okc oke okk oko okp oo- ooa oob ooc ook ooo oop oox op- opa opb opc ope opk opo opp opx ox- oxa oxb oxc oxo oxx p-p paa pab pac pae pak pao pap pax pba pbb pbc pbe pbk pbo pbp pbx pca pcb pcc pce pck pco pcp pcx pea peb pec pee pek peo pep pex pka pkb pkc pke pko pkp poa pob poc poe pok poo pop pox ppa ppb ppc ppe ppk ppo ppp ppx pxc pxe pxk xaa xac xak xap xbc xbe xbx xcb xcp xcx xee xep xex xkb xke xoa xoc xok xoo xop xox xpa xpb xpc xpe xpo xpp xxo xxp xxx