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