import numpy as np

N = int(input())
A = np.array([int(x) for x in input().split()])
B = np.array([int(x) for x in input().split()])
def main(A,B):
    if N == 2:
        if sum(A) != sum(B):
            return -1
        else:
            return abs(A[0] - B[0])
    else:
        if sum(A) < sum(B) or (sum(A) - sum(B)) % (N - 2) != 0:
            return -1
        t = (sum(A) - sum(B)) // (N - 2)
        A -= t
        x = B - A
        if np.all((x >= 0) & (x % 2 == 0)):
            return t
        else:
            return -1
print(main(A,B))