mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

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

    if N == 2:
        if sum(A) != sum(B):
            print(-1)
        else:
            print(abs(A[0] - B[0]))
        exit()

    if A == B:
        print(0)
        exit()

    SA = sum(A)
    SB = sum(B)
    if SA <= SB:
        print(-1)
    else:
        if (SA - SB) % (N-2):
            print(-1)
        else:
            cnt = 0
            ok = 1
            k = (SA - SB) // (N-2)
            for a, b in zip(A, B):
                if a - k > b:
                    ok = 0
                    break
                else:
                    if (b - (a-k)) % 2 != 0:
                        ok = 0
                        break
                    cnt += (b - (a-k)) // 2
            if ok == 0 or cnt != k:
                print(-1)
            else:
                print(k)


if __name__ == '__main__':
    main()