n = int(input())
a = list(map(int, input().split()))
b = list(map(int, input().split()))
if sum(a) < sum(b):
    print(-1)
else:
    c = (sum(a) - sum(b)) // (n - 2)
    for i in range(n):
        if abs(a[i] - b[i]) // (n - 2) > c:
            c = -1
    print(c)