symbolic n;
symbolic c;

R := {[i,j] : 1 <= i <= 10 && 1 <= j <= n};
R;
ac := approximate {[i,j] : exists (lambda0, lambda1,lambda2,lambda3,lambda4 :
	0 <= lambda0, lambda1,lambda2,lambda3,lambda4
	&& c = lambda0-lambda1+ 10 lambda2 - lambda3
	&& i = lambda1-lambda2
	&& j = lambda3-lambda4
	&& n = lambda4)};
ac;

#ac intersection {[i,j] : i = 1 && c = -1}		;
#ac intersection {[i,j] : i = -1 && c = 10}		;
#ac intersection {[i,j] :  j = 1 && c = -1 }		;
#ac intersection {[i,j] : j = -1 && n = 1}		;