n=int(input())
a=list(map(int,input().split()))
b=list(map(int,input().split()))
if n==2:
 if sum(a)!=sum(b):exit(print(-1))
 else:exit(print(abs(a[0]-b[0])))
if sum(a)<sum(b)or(sum(a)-sum(b))%(n-2)!=0:exit(print(-1))
R=(sum(a)-sum(b))//(n-2)
for i in range(n):
 if (b[i]+R-a[i])%2or b[i]+R<a[i]:exit(print(-1))
print(R)