a-a a-b a-c aaa aab aac aaf aap ab- aba abb abc abf abp ac- aca acb acc acf acp af- afa afb afc aff afp ap- apa apb apc apf app b-p baa bab bac baf bap bba bbb bbc bbf bbp bca bcb bcc bcf bcp bfa bfb bfc bff bfp bpa bpb bpc bpf bpp c-- caa cab cac caf cap cba cbb cbc cbf cbp cca ccb ccc ccf ccp cfa cfb cfc cff cfp cpa cpb cpc cpf cpp faa fab fac faf fap fba fbb fbc fbf fbp fca fcb fcc fcf fcp ffa ffc fff ffp fpa fpb fpc fpp p-p paa pab pac paf pap pba pbb pbc pbf pbp pca pcb pcc pcf pcp pfa pfb pfc pff pfp ppa ppb ppc ppf ppp