a-a a-b a-i aaa aab aai aan aap ab- aba abb abi abn abp ai- aia aib aii ain aip an- ana anb ani ann anp ap- apa apb api apn app b-p baa bab bai ban bap bba bbb bbi bbn bbp bi- bia bib bii bin bip bna bnb bni bnn bnp bpa bpb bpi bpn bpp ia- iaa iab iai ian iap iba ibb ibi ibn ibp iia iib iii iin iip in- ina inb ini inn inp ipa ipb ipi ipn ipp n-i naa nab nai nan nap nba nbb nbi nbn nbp nia nib nii nin nip nna nnb nni nnn nnp npa npb npi npn npp p-p paa pab pai pan pap pba pbb pbi pbn pbp pia pib pii pin pip pn- pna pnb pni pnn pnp ppa ppb ppi ppn ppp