#sdpsgssolutions
#A Mindbending Scenario - 80%
#Starter Problems 1

# Open the input and output files.
inputFile = open("bendin.txt", "r")
outputFile = open("bendout.txt", "w")

# Read the input
myInput = inputFile.readline().split()
a = int(myInput[0])
b = int(myInput[1])
c = int(myInput[2])
d = int(myInput[3])
myInput = inputFile.readline().split()
w = int(myInput[0])
x = int(myInput[1])
y = int(myInput[2])
z = int(myInput[3])

# Calculations
awidth = c-a
aheight = d-b
aarea = awidth*aheight
bwidth = y-w
bheight = z-x
barea = bwidth*bheight
totalarea = aarea + barea

if (w<c and x<d) or (a<y and b<z):
 if a<w:
  extrabottomleftx = w

 else:
  extrabottomleftx = a

 if b<x:
  extrabottomlefty = x

 else:
  extrabottomlefty = b

 if c<y:
  extratoprightx = c

 else:
  extratoprightx = y

 if d<z:
  extratoprighty = d

 else:
  extratoprighty = z

 extrawidth = extratoprightx-extrabottomleftx
 extraheight = extratoprighty-extrabottomlefty
 extratotal = extrawidth*extraheight
 totalarea = totalarea-extratotal

# Write the answer to the output file.
outputFile.write(str(totalarea))

# Finally, close the input/output files.
inputFile.close()
outputFile.close()