N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

diff = []

for i in range(N):
    t = B[i] - A[i]

    diff.append(t)

diff.sort()

t = diff[0]

def calc():
    res = 0.0
    for obj in diff:
        if obj == t:
            pass
        else:
            res += (abs(t) + obj) / 2

    return res

res = calc()
result = -1

if res.is_integer():
    r = int(res)
    if abs(t) == r:
        result = r
    else:
        t = t // (N-2) * N
        res = calc()
        if res.is_integer():
            r = int(res)
            if abs(t) == r:
                result = abs(r)

print(result)