#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
    cin >> N;
    vector<int> A(N), B(N);
    for(int i = 0; i < N; ++i)  cin >> A[i];
    for(int i = 0; i < N; ++i)  cin >> B[i];
    ll gap = accumulate(A.begin(), A.end(), 0LL) - accumulate(B.begin(), B.end(), 0LL);
    if(gap < 0){
        cout << -1 << endl;
        return 0;
    }
    if(N == 2){
        if(gap != 0){
            cout << -1 << endl;
        }
        cout <<  max(0, B[0] - A[0]) + max(0, B[1] - A[1]) << endl;
        return 0;
    }
    else if(gap % (N - 2) != 0){
        cout << -1 << endl;
        return 0;
    }

    int ans = gap / (N - 2);
    
    ll sum = 0;
    for(int i = 0; i < N; ++i){
        int need = B[i] - (A[i] - ans);
        if(need < 0 || need % 2 == 1){
            cout << -1 << endl;
            return 0;
        }
        sum += need;
    }
    if(sum != 2 * ans)  ans = -1;
    
    cout << ans << endl;

    return 0;
}