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

if N == 2:
    if A[0] - B[0] == -(A[1] - B[1]):
        print(abs(A[0] - B[0]))
    else:
        print(-1)
elif N > 3:
    print(1/0)
    if (sum(A) - sum(B)) % (N - 2) == 0:
        print((sum(A) - sum(B)) // (N - 2))
    else:
        print(-1)