#!/usr/bin/env python3
# from typing import *

import sys
import io
import math
import collections
import decimal
import itertools
import bisect
import heapq


def input():
    return sys.stdin.readline()[:-1]


# sys.setrecursionlimit(1000000)

# _INPUT = """# paste here...
# """
# sys.stdin = io.StringIO(_INPUT)

INF = 10**10

def solve(N, A, B):
    D = [A[i]-B[i] for i in range(N)]
    s = sum(D)
    
    if N == 2:
        if s != 0:
            return -1
        return abs(D[0])

    else:
        if s % (N-2) != 0:
            return -1
        
        n = s // (N-2)
        for d in D:
            d1 = d - n
            if not (d1 % 2 == 0 and d1 <= 0):
                return -1
        return n




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

print(solve(N, A, B))