/* -*- coding: utf-8 -*-
 *
 * 1120.cc:  No.1120 Strange Teacher - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N], bs[MAX_N];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);

  ll asum = 0, bsum = 0;
  for (int i = 0; i < n; i++) scanf("%d", as + i), asum += as[i];
  for (int i = 0; i < n; i++) scanf("%d", bs + i), bsum += bs[i];

  int d = n - 2;
  ll f = asum - bsum;

  if (d == 0)
    printf("%lld\n", (f == 0) ? abs<ll>(as[0] - bs[0]) : -1);
  else {
    if (f < 0 || f % d != 0) { puts("-1"); return 0; }
    ll r = f / d;
    //printf("d=%d, f=%lld, r=%lld\n", d, f, r);

    ll xsum = 0, ysum = 0;
    for (int i = 0; i < n; i++) {
      // x + y = r, x - y = bi - ai;
      int c = bs[i] - as[i];
      if (r + c < 0 || r - c < 0 || ((r + c) % 1)) { puts("-1"); return 0; }
      xsum += (r + c) / 2, ysum += (r - c) / 2;
    }
    //printf("xsum=%lld, ysum=%lld\n", xsum, ysum);

    if (xsum != r || ysum != r * (n - 1)) { puts("-1"); return 0; }

    printf("%lld\n", r);
  }
  return 0;
}