var
   x1, y1, x2, y2, x3, y3, x4, y4, xll, ll, l2, xr, r1, r2, up, u1, u2, o1, o2, o: integer;
begin

   readln(x1, y1, x2, y2, x3, y3, x4, y4);
   if (x1 < x2) then
      ll := x1
   else
      ll :=x2;
   if (x3 < x4) then
      l2 := x3
   else
      l2 :=  x4;
   if (ll < l2) then
      xll := l2
   else
      xll := ll; //xleft = max(min(x1,x2),min(x3,x4))
   if (x1 > x2) then
      r1 := x1
   else
      r1 := x2;
   if (x3 > x4) then
      r2 := x3
   else
      r2 := x4;
   if (r1 > r2) then
      xr := r2
   else
      xr := r1; //xright = min(max(x1, x2), max(x3, x4))
   if (y1 > y2) then
      u1 := y1
   else
      u1 := y2;
   if (y3 > y4) then
      u2 := y3
   else
      u2 := y4;
   if (u1 > u2) then
      up := u2
   else
      up := u1; //yup = min(max(y1, y2), max(y3, y4))
   if (x1 < x2) then
      o1 := x1
   else
      o1 := x2;
   if (x3 < x4) then
      o2 := x3
   else
      o2 := x4;
   if (o1 < o2) then
      o := o2
   else
      o := o1; //ydown =max(min(y1,y2),min(y3,y4))
   if (((xll > xr) or (up < o)) or ((xll > xr) and (up < o))) then
      writeln('0')
   else
      writeln((xr - xll) * (up - o));
      readln;
end.