def solve():
  ans = 0
  N = int(input())
  A = list(map(int, input().split()))
  B = list(map(int, input().split()))
  if (sum(A)-sum(B))%(N-2)!=0:
    return -1
  cnt = (sum(A)-sum(B))//(N-2)
  B = list(map(lambda x:(x+cnt),B))
  for i in range(N):
    if (B[i]-A[i])%2==1:
      return -1
  return cnt
print(solve())