// Template
#include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <queue>
#include <deque>
#include <stack>
#include <tuple>
#include <map>
#include <set>
#include <algorithm>
#include <utility>
#include <cmath>
#include <complex>
#define rep(i, x) for (int i = 0; i < (x); ++i)
#define rng(i, x, y) for (int i = (x); i < (y); ++i)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define pb push_back
using namespace std;
using ll = long long;
constexpr int inf = 1001001001;
constexpr ll INF = 3003003003003003003;
template <typename T> inline bool chmin(T &x, const T &y) {if (x > y) {x = y; return 1;} return 0;}
template <typename T> inline bool chmax(T &x, const T &y) {if (x < y) {x = y; return 1;} return 0;}
void solve();
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(10);
    solve();
    return 0;
}

// Main Code
void solve() {
    int n;
    cin >> n;
    vector<ll> a(n), b(n);
    rep(i, n) cin >> a[i];
    rep(i, n) cin >> b[i];
    
    if (n == 2) {
        if (a[0] + a[1] == b[0] + b[1]) cout << abs(a[0] - b[0]) << "\n";
        else cout << "-1\n";
        return;
    }
    ll asum = 0, bsum = 0;
    rep(i, n) {
        asum += a[i];
        bsum += b[i];
    }
    if (asum < bsum) {
        cout << "-1\n";
        return;
    }
    if ((asum - bsum) % (n - 2)) {
        cout << "-1\n";
        return;
    }
    ll k = (asum - bsum) / (n - 2);
    vector<ll> ans(n, 0);
    rep(i, n) {
        if ((b[i] - a[i] + k) & 1) {
            cout << "-1\n";
            return;
        }
        ans[i] = (a[i] + k - b[i]) / 2;
        if (ans[i] < 0 || ans[i] > k) {
            cout << "-1\n";
            return;
        }
    }
    cout << k << "\n";
    return;
}