n = int(input())
A = list(map(int, input().split()))
B = list(map(int, input().split()))
tota = sum(A)
totb = sum(B)
if n == 2:
    if tota == totb:
        print(abs(A[0] - B[0]))
    else:
        print(-1)
    exit()
d = tota - totb
if d < 0:
    print(-1)
    exit()
if d % (n - 2) != 0:
    print(-1)
    exit()
cnt = d // (n - 2)
A = [a - cnt for a in A]
tot = sum(max(a - b, 0) for a, b in zip(A, B))
if tot < cnt:
    print(-1)
else:
    print(cnt)