#include <iostream> // cout, endl, cin
#include <string> // string, to_string, stoi
#include <vector> // vector
#include <algorithm> // min, max, swap, sort, reverse, lower_bound, upper_bound
#include <utility> // pair, make_pair
#include <tuple> // tuple, make_tuple
#include <cstdint> // int64_t, int*_t
#include <cstdio> // printf
#include <map> // map
#include <queue> // queue, priority_queue
#include <set> // set
#include <stack> // stack
#include <deque> // deque
#include <unordered_map> // unordered_map
#include <unordered_set> // unordered_set
#include <bitset> // bitset
#include <cctype> // isupper, islower, isdigit, toupper, tolower
#include <iomanip> // setprecision
#include <complex> // complex
#include <math.h> 
#define enld '\n'
#define rep(i,n) for(int i=0; i<(n); i++)
using namespace std;
using ll = long long;
using P = pair<int,int>;
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC optimize("Ofast")
constexpr ll INF = 1e18;
constexpr int inf = 1e9;
constexpr ll mod = 1000000007;
constexpr ll mod2 = 998244353;
const double PI = 3.1415926535897932384626433832795028841971;
const int dx[8] = {1, 0, -1, 0,1,1,-1,-1};
const int dy[8] = {0, 1, 0, -1,1,-1,1,-1};
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
// ---------------------------------------------------------------------------

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N;
    cin >> N;
    vector<int> A(N);
    ll sum_A = 0;
    for(int i=0; i<N; i++){
      cin >> A[i];
      sum_A += A[i];
    }
    vector<int> B(N);
    ll sum_B = 0;
    for(int i=0; i<N; i++){
      cin >> B[i];
      sum_B += B[i];
    }
    if(N == 2){
      if(sum_A == sum_B){
        cout << abs(A[0]-B[0]) << "\n";
      }else{
        cout << -1 << "\n";
      }
      return 0;
    }
    if((sum_A-sum_B)%(N-2) != 0){
      cout << "-1\n";
      return 0;
    }
    ll cnt = (sum_A-sum_B)/(N-2);
    ll now = 0;
    for(int i=0; i<N; i++){
      A[i] -= cnt;
      if(A[i] > B[i] || (B[i]-A[i])%2){
        cout << -1 << "\n";
        return 0;
      }
      now += (B[i]-A[i])/2;
    }
    if(now == cnt){
      cout << now << "\n";
    }else{
      cout << -1 << "\n";
    }
    return 0;
}