import sys
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
INF = 2 ** 63 - 1
mod = 998244353
n = ii()
a = li()

b = li()

time = sum(a) - sum(b)

if time % (n - 2) != 0:
    print(-1)
    exit()

time //= n - 2
cnt = 0
for i in range(n):
    a[i] -= time
    if b[i] < a[i] or (b[i] - a[i]) % 2:
        print(-1)
        exit()
    cnt += (b[i] - a[i]) // 2
if cnt == time:
    print(time)
else:
    print(-1)