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