a-a a-c aaa aac aas aax aay ac- aca acc acs acx acy as- asa asc ass asx asy ax- axa axs axx ay- aya ayc ays ayx c-- caa cac cas cax cay cca ccc ccs ccx csa csc css csx csy cxc cxs cxx cya cyc cys saa sac sas sax say sca scc scs scx ss- ssa ssc sss ssx sxc sxs sy- sya syc sys syx xaa xac xas xcx xsa xsc xss xxx xxy xyy yaa yac yas yax yay yca ycc ycs ycy ysa ysc yss ysy yxa yxy yyc yys yyy