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