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

if N == 2:
    if sum(A) == sum(B):
        print(abs(A[0] - B[0]))
    else:
        print(-1)
elif N > 2:
    if sum(B) > sum(A):
        print(-1)
    elif (sum(A) - sum(B)) % (N - 2) == 0:
        t = (sum(A) - sum(B)) // (N - 2)
        s = 0
        for i in range(N):
            if A[i] - B[i] > t:
                print(-1)
                break
            s += t - (A[i] - B[i])
            if s > t:
                print(-1)
                break
        else:
            print(t)
    else:
        print(-1)