a-a a-b a-c aaa aab aac aan aao aap aar ab- aba abb abc abn abo abp abr ac- aca acb acc acn aco acp acr an- ana anb anc ann ano anp anr aoa aob aoc aon aoo aop aor ap- apa apb apc apn apo app apr ar- ara arb arc arn aro arp arr b-p baa bab bac ban bao bap bar bba bbb bbc bbn bbo bbp bbr bca bcb bcc bcn bco bcp bcr bna bnb bnc bnn bno bnp bnr boa bob boc bon boo bop bor bpa bpb bpc bpn bpo bpp bpr bra brb brn bro brp brr c-- caa cab cac can cao cap car cba cbb cbc cbn cbo cbp cbr cca ccb ccc ccn cco ccp ccr cn- cna cnb cnc cnn cno cnp cnr co- coa cob coc con coo cop cor cpa cpb cpc cpn cpo cpp cpr cra crb crc crn cro crp crr naa nab nac nan nao nap nar nba nbb nbc nbn nbo nbp nbr nca ncb ncc ncn nco ncp ncr nna nnb nnc nnn nno nnp no- noa nob noc non noo nop nor npa npb npc npn npo npp npr nra nrb nrc nrn nro nrp nrr oaa oab oac oan oao oap oar ob- oba obb obc obn obo obp obr oc- oca ocb occ ocn oco ocp ocr on- ona onb onc onn ono onp onr oo- ooa oob ooc oon ooo oop oor op- opa opb opc opn opo opp opr or- ora orb orc orn oro orp orr p-p paa pab pac pan pao pap par pba pbb pbc pbn pbo pbp pbr pca pcb pcc pcn pco pcp pcr pn- pna pnb pnc pnn pno pnp pnr poa pob poc pon poo pop por ppa ppb ppc ppn ppo ppp ppr pra prb prc prn pro prp prr ra- raa rab rac ran rao rap rar rba rbb rbc rbn rbo rbp rbr rca rcb rcc rcn rco rcp rcr rna rnb rnc rnn rno rnp rnr roa rob roc ron roo rop ror rpa rpb rpc rpn rpo rpp rpr rra rrb rrc rrn rrp rrr