a-a a-b a-c aaa aab aac aan aao aap aar aax ab- aba abb abc abn abo abp abr abx ac- aca acb acc acn aco acp acr acx an- ana anb anc ann ano anp anr anx aoa aob aoc aon aoo aop aor aox ap- apa apb apc apn apo app apr apx ar- ara arb arc arn aro arp arr arx ax- axa axn axo axp axr axx b-p baa bab bac ban bao bap bar bax bba bbb bbc bbn bbo bbp bbr bbx bca bcb bcc bcn bco bcp bcr bcx bna bnb bnc bnn bno bnp bnr bnx boa bob boc bon boo bop bor box bpa bpb bpc bpn bpo bpp bpr bpx bra brb brn bro brp brr brx bxb bxn bxo bxx c-- caa cab cac can cao cap car cax cba cbb cbc cbn cbo cbp cbr cbx cca ccb ccc ccn cco ccp ccr ccx cn- cna cnb cnc cnn cno cnp cnr cnx co- coa cob coc con coo cop cor cox cpa cpb cpc cpn cpo cpp cpr cpx cra crb crc crn cro crp crr crx cxc cxo cxp cxr cxx naa nab nac nan nao nap nar nax nba nbb nbc nbn nbo nbp nbr nbx nca ncb ncc ncn nco ncp ncr ncx nna nnb nnc nnn nno nnp no- noa nob noc non noo nop nor nox npa npb npc npn npo npp npr nra nrb nrc nrn nro nrp nrr nrx nxc oaa oab oac oan oao oap oar oax ob- oba obb obc obn obo obp obr obx oc- oca ocb occ ocn oco ocp ocr ocx on- ona onb onc onn ono onp onr onx oo- ooa oob ooc oon ooo oop oor oox op- opa opb opc opn opo opp opr opx or- ora orb orc orn oro orp orr orx ox- oxa oxb oxc oxn oxo oxx p-p paa pab pac pan pao pap par pax pba pbb pbc pbn pbo pbp pbr pbx pca pcb pcc pcn pco pcp pcr pcx pn- pna pnb pnc pnn pno pnp pnr pnx poa pob poc pon poo pop por pox ppa ppb ppc ppn ppo ppp ppr ppx pra prb prc prn pro prp prr prx pxc pxr ra- raa rab rac ran rao rap rar rax rba rbb rbc rbn rbo rbp rbr rbx rca rcb rcc rcn rco rcp rcr rcx rna rnb rnc rnn rno rnp rnr roa rob roc ron roo rop ror rox rpa rpb rpc rpn rpo rpp rpr rpx rra rrb rrc rrn rrp rrr rxp rxr xaa xac xan xap xar xbc xbr xbx xcb xcp xcr xcx xna xnc xno xoa xoc xon xoo xop xor xox xpa xpb xpc xpn xpo xpp xrc xrx xxo xxp xxx