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

up = 0
maxv = 0
for i in range(N):
    maxv = max(maxv, B[i] - A[i])
    up += (B[i] > A[i])

if up != 1 and A != B:
    print(-1)
    exit()

if N == 2:
    if sum(A) == sum(B):
        print(maxv)
    else:
        print(-1)
else:
    for i in range(N):
        if B[i] > A[i]:
            A[i] += maxv
        else:
            A[i] -= maxv

    S = 0
    for i in range(N):
        S += A[i] - B[i]
        if B[i] > A[i]:
            print(-1)
            exit()
    if S % (N - 2) == 0:
        print(S//(N-2) + maxv)
    else:
        print(-1)