n = int(input())
a = [int(i) for i in input().split()]
b = [int(i) for i in input().split()]

li = [0]*n
ans = 0
for i in range(n):
    li[i] = b[i]-a[i]

li.sort(reverse=True)
ans = -li[n-1]

tmp = 0

for i in range(n-1):
    tmp -= li[i]

if ans == tmp:
    print(ans)
elif ans > tmp:
    print(-1)
elif abs(ans-tmp) % (n-2) == 0:
    print(ans+abs(ans-tmp)//(n-2))
else:
    print(-1)