#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using P = pair<int, int>;
using PL = pair<lint, lint>;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
#define ALL(a)  (a).begin(),(a).end()
constexpr int MOD = 1000000007;
constexpr int INF = 2147483647;
void yes(bool expr) {cout << (expr ? "Yes" : "No") << "\n";}
int main()
{
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  lint N;
  cin >> N;
  vector<lint> A(N);
  REP(i, N) cin >> A[i];
  vector<lint> B(N);
  REP(i, N) cin >> B[i];
  lint Asum = 0;
  REP(i, N) Asum += A[i];
  lint Bsum = 0;
  REP(i, N) Bsum += B[i];
  if(Asum < Bsum) {
    cout << -1 << endl;
    return 0;
  }
  if(N == 2) {
    if(Asum != Bsum) {
      cout << -1 << endl;
      return 0;
    }
    cout << abs(A[0] - B[0]) << endl;
    return 0;
  }
  if((Asum - Bsum)%(N-2) != 0) {
    cout << -1 << endl;
    return 0;
  }
  lint cnt = (Asum - Bsum) / (N-2);
  REP(i, N) A[i] -= cnt;
  REP(i, N) {
    if(A[i] > B[i] || (B[i] - A[i])%2 != 0) {
      cout << -1 << endl;
      return 0;
    }
  }
  cout << cnt << endl;
}