a-a a-b a-c aaa aab aac aak aap aay ab- aba abb abc abk abp aby ac- aca acb acc ack acp acy aka akb akc akk akp ap- apa apb apc apk app apy ay- aya ayc ayk ayp b-p baa bab bac bak bap bay bba bbb bbc bbk bbp bby bca bcb bcc bck bcp bcy bka bkb bkc bkk bkp bpa bpb bpc bpp bpy by- bya byc byk byp c-- caa cab cac cak cap cay cba cbb cbc cbk cbp cby cca ccb ccc cck ccp cka ckb ckc cky cpa cpb cpc cpk cpp cya cyb cyc cyk cyp ka- kaa kab kac kak kap kay kba kbb kbc kbk kbp kca kcb kcc kck kcp kkb kkc kkk kkp kky kpa kpc kpk kpp kya kyc kyp p-p paa pab pac pak pap pay pba pbb pbc pbk pbp pby pca pcb pcc pck pcp pka pkb pkc pkp pky ppa ppb ppc ppk ppp py- pya pyb pyc pyk yaa yab yac yak yap yay ybc ybp yby yca ycc ycp ycy yka ykk ypa yyb yyc yyy