#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  cin >> N;
  vector<int> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  vector<int> B(N);
  for (int i = 0; i < N; i++){
    cin >> B[i];
  }
  if (N == 2){
    if (A[0] + A[1] != B[0] + B[1]){
      cout << -1 << endl;
    } else {
      cout << abs(B[0] - A[0]) << endl;
    }
  } else {
    long long A_sum = 0;
    for (int i = 0; i < N; i++){
      A_sum += A[i];
    }
    long long B_sum = 0;
    for (int i = 0; i < N; i++){
      B_sum += B[i];
    }
    long long diff = A_sum - B_sum;
    if (diff < 0 || diff % (N - 2) != 0){
      cout << -1 << endl;
    } else {
      for (int i = 0; i < N; i++){
        A[i] -= diff / (N - 2);
      }
      bool ok = true;
      for (int i = 0; i < N; i++){
        if (A[i] > B[i]){
          ok = false;
        }
        if ((A[i] - B[i]) % 2 != 0){
          ok = false;
        }
      }
      if (!ok){
        cout << -1 << endl;
      } else {
        cout << diff / (N - 2) << endl;
      }
    }
  }
}