#include <iostream>
#include <vector>
using namespace std;
using ll = long long;
using vi = vector<int>;
void ins() {}
template<class T,class... Rest>void ins(T& v,Rest&... rest){cin>>v;ins(rest...);}

#define rep(i,n) for(int i=0,_i=(n);i<_i;++i)

// ========== debug ==========
template<class T>ostream& operator<<(ostream& os,const vector<T>& vec){os<<"{";for(size_t i=0;i<vec.size();++i)os<<(i?", ":"")<<vec[i];os<<"}";return os;}
ostream& operator<<(ostream& os,const vector<char>&v){for(size_t i=0;i<v.size();++i)os<<v[i];return os;}
template<class T1,class T2>ostream& operator<<(ostream& os,const pair<T1,T2>& rhs){os<<"("<<rhs.first<<", "<<rhs.second<<")";return os;}

#ifdef LOCAL
void debug() {cerr << "\n";}
template<class First> void debug(const First& first) {cerr<<first<<"\n";}
template<class First, class... Rest> void debug(const First& first, const Rest&... rest) {cerr<<first<<",";debug(rest...);}
void debug2() {cerr << "\n";}
template<class First> void debug2(const First& first) {cerr<<first<<" ";}
template<class First, class... Rest> void debug2(const First& first, const Rest&... rest) {cerr<<first<<" ";debug2(rest...);}
#else
#define debug(...) 42
#define debug2(...) 42
#endif
// ===========================

int main() {
  int N;
  ins(N);

  vi A(N), B(N);
  rep(i, N) { cin >> A[i]; }
  rep(i, N) { cin >> B[i]; }

  int max_diff = -1e9;
  bool is_same = true;
  vi diff(N);
  rep(i, N) {
    max_diff = max(max_diff, A[i] - B[i]);
    diff[i] = A[i] - B[i];
    if (diff[i] != 0)
      is_same = false;
  }
  if (max_diff < 0) {
    cout << -1 << endl;
    return 0;
  }
  if (is_same) {
    cout << 0 << endl;
    return 0;
  }
  ll sum_diff = 0;
  debug(diff);
  rep(i, N) {
    diff[i] -= max_diff;
    if (diff[i] % 2 != 0) {
      cout << -1 << endl;
      return 0;
    }
    sum_diff += abs(diff[i]) / 2;
  }
  if (sum_diff == max_diff)
    cout << max_diff << endl;
  else if (sum_diff > max_diff)
    cout << -1 << endl;
  else {
    debug(max_diff, sum_diff, max_diff - sum_diff);
    // (max_diff - sum_diff) * 2 を全体に分配しなければならない
    // で、それをゼロにできればok
    // 直感的には、ある1つを除いて他に分配、その1つに足す操作をしていけば良さそう

    if ((max_diff - sum_diff) % ((N/2)-1) != 0) {
      cout << -1 << endl;
      return 0;
    }
    cout << max_diff + (max_diff - sum_diff)/ ((N/2)-1) << endl;
  }
  return 0;
}

// 全員-1して、ある生徒だけ+2と捉え直す。
// 全員0以下になるまで操作を行う。そこから+2していく