a-a a-b aaa aab aae aao aap ab- aba abb abe abo abp aea aeb aee aeo aep aoa aob aoe aoo aop ap- apa apb ape apo app b-p baa bab bae bao bap bba bbb bbe bbo bbp be- bea beb bee beo bep boa bob boe boo bop bpa bpb bpe bpo bpp eaa eab eae eao eap eba ebb ebe ebo ebp eea eeb eee eeo eep eo- eoa eob eoe eoo eop ep- epa epb epe epo epp oaa oab oae oao oap ob- oba obb obe obo obp oea oeb oee oeo oep oo- ooa oob ooo oop op- opa opb ope opo opp p-p paa pab pae pao pap pba pbb pbe pbo pbp pea peb pee peo pep poa pob poe poo pop ppa ppb ppe ppo ppp