import sys

sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


N = I()
A,B = LI(),LI()

sum_A = sum(A)
sum_B = sum(B)

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

if sum_A < sum_B or (sum_A-sum_B) % (N-2) != 0:
    print(-1)
    exit()

M = (sum_A-sum_B)//(N-2)
A = [A[i]-M for i in range(N)]

for i in range(N):
    a,b = A[i],B[i]
    if a > b or (b-a) % 2 != 0:
        print(-1)
        break
else:
    print(M)