#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef long double ld;
typedef pair<int,int> P;
constexpr int mod = 1e9+7;


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

  if (n == 2) {
    if (a[0] + a[1] != b[1] + b[0]) cout << -1 << endl;
    else cout << abs(a[0] - b[0]) << endl;
    return 0;
  }

  ll suma = 0, sumb = 0;
  for (int i = 0; i < n; i++) suma += a[i], sumb += b[i];
  if (suma < sumb || (suma - sumb) % (n - 2) != 0) {
    cout << -1 << endl;
    return 0;
  }

  ll v = (suma - sumb) / (n - 2);
  ll cnt = 0;
  for (int i = 0; i < n; i++) a[i] -= v;
  for (int i = 0; i < n; i++) {
    int d = b[i] - a[i];
    if (d % 2 == 1 || d < 0) {
      cout << -1 << endl;
      return 0;
    }
    cnt += d;
  }
  if (cnt != 2LL * v) cout << -1 << endl;
  else cout << v << endl; 
  return 0;
}