#include <iostream>
#include <algorithm>
#include <vector>
#include <deque>
#include <queue>
#include <set>
#include <ctime>
#include <map>
#include <boost/multiprecision/cpp_int.hpp>
#include <string>

using namespace std;
using ll = long long;
namespace mp = boost::multiprecision;

int main()
{
  ll N;
  cin >> N;
  ll a_sum = 0;
  ll b_sum = 0;
  vector<ll> A(N);
  vector<ll> B(N);
  for (size_t i = 0; i < N; i++)
  {
      cin >> A[i];
      a_sum += A[i];
  }
  for (size_t i = 0; i < N; i++)
  {
      cin >> B[i];
      b_sum += B[i];
  }

  ll total = 0;
  vector<ll> diffs(N);
  for (size_t i = 0; i < N; i++)
  {
      diffs[i] = B[i] - A[i];
      total += B[i] - A[i];
  }
  if (N == 2){
      if (total == 0){
        ll positive_sum = 0;
        for(int i = 0; i < N;i++){
            if (diffs[i] > 0){
                positive_sum += diffs[i];
            }
        }
        cout << positive_sum << endl;
      }else{
          cout << -1 << endl;
      }
  }else{
    // cout << total % (N-2) << endl;
    if (total % (N-2) != 0){
        cout << -1 << endl;
    }else{
        bool can_make = true;
        for(int i = 0; i < N;i++){
            diffs[i] = diffs[i] + total/(N-2);
            if (diffs[i] > 0 || abs(diffs[i]) % 2 != 0){
                can_make = false;
            }
        }
        if (can_make){
            cout << - total/(N-2) << endl;;
        }else{
            cout << -1 << endl;
        }
    }

  }
  return 0;
}