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]
res = 0.0

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

if res.is_integer():
    r = int(res)
    if abs(t) == r:
        print(r)
    elif (r - abs(t)) % (N - 1) == 0:
        print(r + (r - abs(t)) // (N - 1))
    else:
        print(-1)
else:
    print(-1)