a-a a-b aaa aab aak aap aay ab- aba abb abk abp aby aka akb akk akp ap- apa apb apk app apy ay- aya ayk ayp b-p baa bab bak bap bay bba bbb bbk bbp bby bka bkb bkk bkp bpa bpb bpp bpy by- bya byk byp ka- kaa kab kak kap kay kba kbb kbk kbp kkb kkk kkp kky kpa kpk kpp kya kyp p-p paa pab pak pap pay pba pbb pbk pbp pby pka pkb pkp pky ppa ppb ppk ppp py- pya pyb pyk yaa yab yak yap yay ybp yby yka ykk ypa yyb yyy