#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

long long solve(vector<int> c) {
  int n = c.size();

  sort(c.begin(), c.end());
  if (!c[0] && !c[n-1])
    return 0;

  if (n == 2) {
    if (-c[0] == c[1]) return c[1];
    else return -1;
  }
  
  long long sum = 0;
  REP (i, n) sum += c[i];
  if (sum >= 0) return -1;
  if (abs(sum) % (n-2)) return -1;

  long long d = abs(sum) / (n-2);
  long long cnt = 0;

  REP (i, n) {
    if ((c[i] + d) % 2) return -1;
    long long x = (c[i] + d) / 2;
    if (x < 0 || x > d) return -1;
    cnt += x;
  }
  return cnt == d ? d : -1;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  cin >> n;

  vector<int> a(n), b(n), c(n);
  REP (i, n) cin >> a[i];
  REP (i, n) cin >> b[i];
  REP (i, n) c[i] = b[i] - a[i];

  cout << solve(c) << endl;
  
  return 0;
}