n = int(input())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
if n == 2:
    if sum(a) == sum(b):
        print(abs(a[0] - b[0]))
    else:
        print(-1)
else:
    t = sum(a) - sum(b)
    if t >= 0 and t % (n - 2) == 0:
        t //= n - 2
        res = 0
        for i in range(n):
            k = b[i] - a[i] + t
            if k < 0:
                print(-1)
                break
            res += k
        else:
            if res // 2 == t:
                print(t)
            else:
                print(-1)
    else:
        print(-1)