a-a a-b a-c aaa aab aac aap aay ab- aba abb abc abp aby ac- aca acb acc acp acy ap- apa apb apc app apy ay- aya ayc ayp b-p baa bab bac bap bay bba bbb bbc bbp bby bca bcb bcc bcp bcy bpa bpb bpc bpp bpy by- bya byc byp c-- caa cab cac cap cay cba cbb cbc cbp cby cca ccb ccc ccp cpa cpb cpc cpp cya cyb cyc cyp p-p paa pab pac pap pay pba pbb pbc pbp pby pca pcb pcc pcp ppa ppb ppc ppp py- pya pyb pyc yaa yab yac yap yay ybc ybp yby yca ycc ycp ycy ypa yyb yyc yyy