have(ali,bac1).
throat(ali,red).
throat(reza,pink).
have(reza,bac2).
stain(bac1,grampos).
stain(bac2,gramneg).
morphology(bac1,coccus).
morphology(bac2,sarcina).
growth(bac1,chain).
growth(bac2,not_chain).
strep_throat(X):-infection(X),
	         streptococcus(Y),
		 have(X,Y).
infection(X):-throat(X,red).
streptococcus(X):-stain(X,grampos),
		  morphology(X,coccus),
		  growth(X,chain).