#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define DUMP(x) cout << #x << " = " << (x) << endl;
#define FOR(i, m, n) for (ll i = m; i < n; i++)
#define IFOR(i, m, n) for (ll i = n - 1; i >= m; i--)
#define REP(i, n) FOR(i, 0, n)
#define IREP(i, n) IFOR(i, 0, n)
#define FOREACH(x, a) for (auto&(x) : (a))
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) ll(x.size())

void no() {
  cout << -1 << endl;
  exit(0);
}

int main() {
  ll n;
  cin >> n;
  vector<ll> a(n), b(n);
  REP(i, n) { cin >> a[i]; }
  REP(i, n) { cin >> b[i]; }

  ll sum = 0;
  REP(i, n) { sum += a[i] - b[i]; }

  if (n == 2) {
    if (sum != 0) {
      no();
    }
    cout << abs(a[0] - b[0]) << endl;
    return 0;
  }

  if (sum % (n - 2) != 0) {
    no();
  }
  ll ans = sum / (n - 2);

  REP(i, n) {
    ll d = b[i] - a[i] + ans;
    if (d < 0 || d % 2 == 1) {
      no();
    }
  }
  cout << ans << endl;
}