#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<long long> vl;
#define INF __INT32_MAX__

int main() {
    int N;
    cin >> N;
    vi A(N), B(N);
    ll suma = 0, sumb = 0;
    rep(i, N) {
        cin >> A[i];
        suma += A[i];
    }
    rep(i, N) {
        cin >> B[i];
        sumb += B[i];
    }

    if (N == 2) {
        if (A[0] + A[1] != B[0] + B[1]) {
            cout << -1 << endl;
        } else {
            cout << abs(A[0] - B[0]) << endl;
        }
        return 0;
    }

    if (suma < sumb || (suma - sumb) % (N - 2) != 0) {
        cout << -1 << endl;
        return 0;
    }

    bool ok = true;
    ll v = (suma - sumb) / (N - 2);
    ll sump = 0;
    rep(i, N) {
        ll p = B[i] - (A[i] - v);
        if (p < 0 || p % 2 != 0) {
            ok = false;
            break;
        }
        sump += p;
    }

    if (sump != 2 * v) ok = false;

    if (!ok) {
        cout << -1 << endl;
    } else {
        cout << v << endl;
    }
}