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

left = max(min(x1, x2), min(x3, x4))
right = min(max(x1, x2), max(x3, x4))

bottom = max(min(y1, y2), min(y3, y4))
top = min(max(y1, y2), max(y3, y4))

width = max(0, right - left)
height = max(0, top - bottom)

print(width * height)