rps($x$;$y$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$$x$=$_{2}$2 $\wedge_{2}$ $y$=$_{2}$0 $\vee_{2}$ $x$=$_{2}$1 $\wedge_{2}$ $y$=$_{2}$2 $\vee_{2}$ $x$=$_{2}$0 $\wedge_{2}$ $y$=$_{2}$1