import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N = int(input())
	A = getlist()
	B = getlist()
	for i in range(N):
		A[i] -= B[i]

	if N == 2:
		if sum(A) == 0:
			print(abs(A[0]))
		else:
			print(-1)
		return

	dif = sum(A)
	if dif % (N - 2) != 0:
		print(-1)
		return

	n = int(dif // (N - 2))
	# 2 * aplha = n - A[i]
	cnt = 0
	for i in range(N):
		if (n - A[i]) % 2 == 1 or n - A[i] < 0:
			print(-1)
			return
		cnt += int((n - A[i]) // 2)

	if cnt == n:
		print(n)
	else:
		print(-1)


if __name__ == '__main__':
	main()