#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
const int INF = 0x3f3f3f3f;
const ll LINF = 0x3f3f3f3f3f3f3f3fLL;
const double EPS = 1e-8;
const int MOD = 1000000007;
// const int MOD = 998244353;
const int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1};
const int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U> inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U> inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int n; cin >> n;
  vector<ll> a(n), b(n);
  REP(i, n) cin >> a[i];
  REP(i, n) cin >> b[i];
  ll x = 0;
  REP(i, n) x += a[i] - b[i];
  if (n == 1) {
    cout << (a[0] >= b[0] ? a[0] - b[0] : 0) << '\n';
    return 0;
  } else if (n == 2) {
    cout << (x == 0 ? 0 : -1) << '\n';
    return 0;
  }
  if (x < 0 || x % (n - 2) != 0) {
    cout << "-1\n";
    return 0;
  }
  x /= n - 2;
  ll ans = 0;
  REP(i, n) {
    a[i] -= x;
    if (a[i] > b[i] || (b[i] - a[i]) % 2 == 1) {
      cout << "-1\n";
      return 0;
    }
    ans += (b[i] - a[i]) / 2;
  }
  cout << (x == ans ? x : -1) << '\n';
  return 0;
}