import sys
from sys import stdin
from fractions import Fraction
import math
from math import ceil, floor, sqrt, pi, factorial, gcd
from copy import deepcopy
from collections import Counter, deque, defaultdict
from heapq import heapify, heappop, heappush
from itertools import accumulate, product, combinations, combinations_with_replacement, permutations
from bisect import bisect, bisect_left, bisect_right
from functools import reduce, lru_cache
from decimal import Decimal, getcontext, ROUND_HALF_UP
def i_input(): return int(stdin.readline())
def i_map(): return map(int, stdin.readline().split())
def i_list(): return list(i_map())
def s_input(): return stdin.readline()[:-1]
def s_map(): return s_input().split()
def s_list(): return list(s_map())
def lcm(a, b): return a * b // gcd(a, b)
def get_distance(x1, y1, x2, y2):
	  d = sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)
	  return d
def rotate(table):
   	  n_fild = []
   	  for x in zip(*table[::-1]):
   	  	  n_fild.append(x)
   	  return n_fild
sys.setrecursionlimit(10 ** 7)
INF = float('inf')
MOD = 10 ** 9 + 7
MOD2 = 998244353
alpa = 'abcdefghijklmnopqrstuvwxyz'
ALPA = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'


def main():
   
   N = int(input())
   A = i_list()
   B = i_list()
   
   Asum = sum(A)
   Bsum = sum(B)
   
   if (Asum - Bsum) % (N-2) != 0:
   	  print(-1)
   	  exit()
   
   cost = (Asum - Bsum) // (N-2)
   
   score = 0
   for i in range(N):
   	  point = B[i] - A[i]
   	  if point % 2 != cost % 2:
   	  	  print(-1)
   	  	  exit()
   	  if point >= 0:
   	  	  amari = cost - point
   	  	  if amari < 0:
   	  	  	  print(-1)
   	  	  	  exit()
   	  	  score += point + amari // 2
   	  else:
   	  	  amari = (cost + point) // 2
   	  	  if amari < 0:
   	  	  	  print(-1)
   	  	  	  exit()
   	  	  score += amari
   
   if score == cost:
   	  print(cost)
   else:
   	  print(-1)
   
   
if __name__ == '__main__':
    main()