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

SA, SB = sum(A), sum(B)

if N == 2:
    if SA == SB:
        print(abs(A[0] - B[0]))
    else:
        print(-1)
else:
    if (SA - SB) % (N - 2):
        print(-1)
        exit()
    n = (SA - SB) // (N - 2)
    for i in range(N):
        A[i] -= n 

    for i in range(N):
        if B[i] - A[i] < 0 or (B[i] - A[i]) % 2:
            print(-1)
            exit()
    print(n)