x1 = int(input())
y1 = int(input())
x2 = int(input())
y2 = int(input())
x3 = int(input())
y3 = int(input())
x4 = int(input())
y4 = int(input())

if x4 > x1 and y4 > y1 and x3 <= x1 and y3 <= y1: S = (x4 - x1) * (y4 - y1)
elif x1 > x4 and y1 > y4 and x1 <= x3 and y1 <= y3: S = (x1 - x4) * (y1 - y4)
elif x2 > x3 and y2 > y3 and x1 <= x2 and y1 <= y2: S = (x2 - x3) * (y2 - y3)
else: S = 0
print(S)