#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
typedef long long ll;

int main() {
    int n;
    cin >> n;
    vector<int> a(n), b(n);
    ll x = 0, y = 0;
    for (int i = 0; i < n; i++) {
        cin >> a[i];
        x += a[i];
    }
    for (int i = 0; i < n; i++) {
        cin >> b[i];
        y += b[i];
    }

    if (n == 2) {
        if (x == y) {
            cout << abs(a[0] - b[0]) << endl;
        } else {
            cout << -1 << endl;
        }
    } else {
        if (y <= x && (x - y) % (n - 2) == 0) {
            ll times = (x - y) / (n - 2);

            bool ok = true;
            ll remain = times;
            for (int i = 0; i < n; i++) {
                if (a[i] % 2 != (b[i] + times) % 2)ok = false;
                if (a[i] - times > b[i])ok = false;
                remain -= (b[i] - (a[i] - times)) / 2;
            }

            cout << (ok && remain == 0 ? times : -1) << endl;
        } else {
            cout << -1 << endl;
        }
    }
    return 0;
}