a-a a-b a-c aaa aab aac aak aao aap aay ab- aba abb abc abk abo abp aby ac- aca acb acc ack aco acp acy aka akb akc akk ako akp aoa aob aoc aok aoo aop ap- apa apb apc apk apo app apy ay- aya ayc ayk ayo ayp b-p baa bab bac bak bao bap bay bba bbb bbc bbk bbo bbp bby bca bcb bcc bck bco bcp bcy bka bkb bkc bkk bko bkp boa bob boc bok boo bop boy bpa bpb bpc bpo bpp bpy by- bya byc byk byo byp c-- caa cab cac cak cao cap cay cba cbb cbc cbk cbo cbp cby cca ccb ccc cck cco ccp cka ckb ckc cko cky co- coa cob coc cok coo cop coy cpa cpb cpc cpk cpo cpp cya cyb cyc cyk cyo cyp ka- kaa kab kac kak kao kap kay kba kbb kbc kbk kbo kbp kca kcb kcc kck kcp kkb kkc kkk kkp kky koa kob koc kok koo kop koy kpa kpc kpk kpo kpp kya kyc kyo kyp oaa oab oac oak oao oap ob- oba obb obc obk obo obp oby oc- oca ocb occ ock oco ocp oka okb okc okk oko okp oo- ooa oob ooc ook ooo oop op- opa opb opc opk opo opp opy oya oyo p-p paa pab pac pak pao pap pay pba pbb pbc pbk pbo pbp pby pca pcb pcc pck pco pcp pka pkb pkc pko pkp pky poa pob poc pok poo pop poy ppa ppb ppc ppk ppo ppp py- pya pyb pyc pyk pyo yaa yab yac yak yao yap yay ybc ybp yby yca ycc yco ycp ycy yka ykk yob yoc yok yoo yop yoy ypa ypo yyb yyc yyy