a-a a-b a-c aaa aab aac aae aan aao aap ab- aba abb abc abe abn abo abp ac- aca acb acc ace acn aco acp aea aeb aec aee aen aeo aep an- ana anb anc ane ann ano anp aoa aob aoc aoe aon aoo aop ap- apa apb apc ape apn apo app b-p baa bab bac bae ban bao bap bba bbb bbc bbe bbn bbo bbp bca bcb bcc bce bcn bco bcp be- bea beb bec bee ben beo bep bna bnb bnc bne bnn bno bnp boa bob boc boe bon boo bop bpa bpb bpc bpe bpn bpo bpp c-- caa cab cac cae can cao cap cba cbb cbc cbe cbn cbo cbp cca ccb ccc cce ccn cco ccp ce- cea ceb cec cee cen ceo cep cn- cna cnb cnc cne cnn cno cnp co- coa cob coc coe con coo cop cpa cpb cpc cpe cpn cpo cpp eaa eab eac eae ean eao eap eba ebb ebc ebe ebn ebo ebp ec- eca ecb ecc ece ecn eco eea eeb eec eee een eeo eep en- ena enb enc ene enn eno enp eo- eoa eob eoc eoe eon eoo eop ep- epa epb epc epe epn epo epp naa nab nac nae nan nao nap nba nbb nbc nbe nbn nbo nbp nca ncb ncc nce ncn nco ncp ne- nea neb nec nee nen neo nep nna nnb nnc nne nnn nno nnp no- noa nob noc noe non noo nop npa npb npc npe npn npo npp oaa oab oac oae oan oao oap ob- oba obb obc obe obn obo obp oc- oca ocb occ ocn oco ocp oea oeb oec oee oen oeo oep on- ona onb onc one onn ono onp oo- ooa oob ooc oon ooo oop op- opa opb opc ope opn opo opp p-p paa pab pac pae pan pao pap pba pbb pbc pbe pbn pbo pbp pca pcb pcc pce pcn pco pcp pea peb pec pee pen peo pep pn- pna pnb pnc pne pnn pno pnp poa pob poc poe pon poo pop ppa ppb ppc ppe ppn ppo ppp