from sys import exit
n = int(input())
a = list(map(int, input().split()))
b = list(map(int, input().split()))

if n == 2:
	if sum(a) == sum(b):
		print(abs(a[0] - b[0]))
	else:
		print(-1)
	exit()

s = sum(a) - sum(b)
if s % (n-2) != 0:
	print(-1)	
else:
	k = s // (n-2)
	for x, y in zip(a, b):
		z = y - x + k
		if z < 0 or z%2 != 0:
			print(-1)
			break
	else:
		print(k)