""" day 1 """

import fileinput

left = []
right = []

for line in fileinput.input():
    a, b = line.split()
    left.append(int(a))
    right.append(int(b))

left = sorted(left)
right = sorted(right)

total = 0

for a,b in zip(left,right):
    total += abs(a-b)

print(total)