n = int(input())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
if n == 2:
    if sum(a) != sum(b):
        print(-1)
    else:
        print(abs(a[0] - b[0]))
else:
    d = sum(a) - sum(b)
    if d < 0 or d % (n - 2) != 0:
        print(-1)
    else:
        d //= n - 2
        s = 0
        for i in range(n):
            s += max(0, b[i] - a[i])
        if s > d or (d - s) % 2:
            print(-1)
        else:
            print(d)