gistfile1.pas

var 
	x1, x2, x3, x4, y1, y2, y3, y4, t, s : integer;

begin
	x1 := 1; x2 := 3; y1 := 1; y2 := 3;
	x3 := 2; x4 := 4;
	y3 := 2; y4 := 4;

	s := 0;

	if x1 > x2 then begin
		t := x1;
		x1 := x2;
		x2 := t;
	end;

	if x3 > x4 then begin
		t := x3;
		x3 := x4;
		x4 := t;
	end;

	if y1 > y2 then begin
		t := y1;
		y1 := y2;
		y2 := t;
	end;

	if y3 > y4 then begin
		t := y3;
		y3 := y4;
		y4 := t;
	end;

	if (x3 > x1) and (x3 < x2) and (y3 > y1) and (y3 < y2) then begin
		s := (x2-x3) * (y2-y3);
	end;

	if (x4 > x1) and (x4 < x2) and (y4 > y1) and (y4 < y2) then begin
		s := (x4-x1) * (y4-y1);
	end;

	if (x3 > x1) and (x3 < x2) and (y4 > y1) and (y4 < y2) then begin
		s := (x2-x3) * (y4-y1);
	end;

	if (x4 > x1) and (x4 < x2) and (y3 > y1) and (y3 < y2) then begin
		s := (x4-x1) * (y2-y3);
	end;

	writeln(s);
end.