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


def is_impossible(b):
    if b:
        print(-1)
        exit()


if N == 2:
    print(abs(A[0] - B[0]) if sum(A) == sum(B) else -1)
    exit()

is_impossible((sum(A) - sum(B)) % (N - 2))

x = (sum(A) - sum(B)) // (N - 2)
is_impossible(x < 0)

C = [B[i] - (A[i] - x) for i in range(N)]
is_impossible(any(c < 0 or c % 2 for c in C))

print(x)