#include <iostream>
#include <numeric>
#include <vector>

using lint = long long;

void fail() {
    std::cout << -1 << "\n";
    std::exit(0);
}

void solve() {
    int n;
    std::cin >> n;

    std::vector<lint> xs(n), ys(n);
    for (auto& x : xs) std::cin >> x;
    for (auto& y : ys) std::cin >> y;

    auto xsum = std::accumulate(xs.begin(), xs.end(), 0LL);
    auto ysum = std::accumulate(ys.begin(), ys.end(), 0LL);

    if (n == 2) {
        if (xsum != ysum) fail();
        std::cout << std::abs(xs[0] - ys[0]) << "\n";
        return;
    }

    if (xsum < ysum || (xsum - ysum) % (n - 2) != 0) fail();

    auto ope = (xsum - ysum) / (n - 2);
    lint need = 0;
    for (int i = 0; i < n; ++i) {
        xs[i] -= ope;
        if (xs[i] > ys[i] || (ys[i] - xs[i]) % 2 != 0) fail();
        need += (ys[i] - xs[i]) / 2;
    }

    if (need != ope) fail();

    std::cout << ope << "\n";
}

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

    solve();

    return 0;
}