begin%STDB%

ship():-	i=1,
	 	x1-t=20,y1=20,
		x2-t=30,y2=25,
		t>=0,t<=25,
		p=-1,s=-1.

torpedo():-	i=1,
		x1=45,y1+t=45,
		x2=48,y2+t=51,
		t>=0,t<=25,
		p=-1,s=-1.

hit():-		ship() * torpedo().

end%STDB%