N = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))

mx = 0
for a, b in zip(A, B):
    mx = max(mx, a - b)

ans = 0
for a, b in zip(A, B):
    ans += mx - (a - b)

print(mx if ans == mx * 2 else -1)