I,S=input,sum
n=int(I())
def L():return list(map(int,I().split()))
a,b=L(),L()
if n==2:
 if S(a)!=S(b):exit(print(-1))
 else:exit(print(abs(a[0]-b[0])))
if S(a)<S(b)or(S(a)-S(b))%(n-2):exit(print(-1))
R=(S(a)-S(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)