a-a a-b a-c aaa aab aac aan aao aap ab- aba abb abc abn abo abp ac- aca acb acc acn aco acp an- ana anb anc ann ano anp aoa aob aoc aon aoo aop ap- apa apb apc apn apo app b-p baa bab bac ban bao bap bba bbb bbc bbn bbo bbp bca bcb bcc bcn bco bcp bna bnb bnc bnn bno bnp boa bob boc bon boo bop bpa bpb bpc bpn bpo bpp c-- caa cab cac can cao cap cba cbb cbc cbn cbo cbp cca ccb ccc ccn cco ccp cn- cna cnb cnc cnn cno cnp co- coa cob coc con coo cop cpa cpb cpc cpn cpo cpp naa nab nac nan nao nap nba nbb nbc nbn nbo nbp nca ncb ncc ncn nco ncp nna nnb nnc nnn nno nnp no- noa nob noc non noo nop npa npb npc npn npo npp oaa oab oac oan oao oap ob- oba obb obc obn obo obp oc- oca ocb occ ocn oco ocp on- ona onb onc onn ono onp oo- ooa oob ooc oon ooo oop op- opa opb opc opn opo opp p-p paa pab pac pan pao pap pba pbb pbc pbn pbo pbp pca pcb pcc pcn pco pcp pn- pna pnb pnc pnn pno pnp poa pob poc pon poo pop ppa ppb ppc ppn ppo ppp