a-a a-b aaa aab aak aao aap aas ab- aba abb abk abo abp abs aka akb akk ako akp aks aoa aob aok aoo aop aos ap- apa apb apk apo app aps as- asa asb ask aso asp ass b-p baa bab bak bao bap bas bba bbb bbk bbo bbp bbs bka bkb bkk bko bkp bks boa bob bok boo bop bos bpa bpb bpo bpp bps bsa bsb bsk bso bsp bss ka- kaa kab kak kao kap kas kba kbb kbk kbo kbp kbs kkb kkk kkp kks koa kob kok koo kop kos kpa kpk kpo kpp kps ksa ksb ksk kso ksp kss oaa oab oak oao oap oas ob- oba obb obk obo obp obs oka okb okk oko okp oks oo- ooa oob ook ooo oop oos op- opa opb opk opo opp ops os- osa osb osk oso osp oss p-p paa pab pak pao pap pas pba pbb pbk pbo pbp pbs pka pkb pko pkp pks poa pob pok poo pop pos ppa ppb ppk ppo ppp pps ps- psa psb psk pso psp pss saa sab sak sao sap sas sba sbb sbk sbo sbp sbs sk- ska skb skk sko skp sks soa sob sok soo sop sos spa spb spk spo spp sps ss- ssa ssb ssk sso ssp sss