import sys
input=lambda: sys.stdin.readline().rstrip()
n=int(input())
A=[int(i) for i in input().split()]
B=[int(i) for i in input().split()]

if n==2:
	if sum(A)==sum(B):
		print(abs(A[0]-B[0]))
	else:
		print(-1)
else:
	d=sum(A)-sum(B)
	if d<0 or d%(n-2)!=0:
		print(-1)
	else:
		ans=d//(n-2)
		ct=0
		Chk=True
		for i in range(n):
			if (B[i]-A[i]+ans)%2!=0 or (B[i]-A[i]+ans)<0:
				Chk=False
			ct+=(B[i]-A[i]+ans)//2
		if Chk==False or ct!=ans:
			print(-1)
		else:
			print(ans)