#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using P = pair<int, int>;
int main()
{
    int n;
    cin >> n;
    vector<int> a(n);
    vector<int> 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 << "-1" << endl;
        else
            cout << abs(a[0] - b[0]) << endl;
        return 0;
    }
    ll sa = 0, sb = 0, v = 0;
    rep(i, n) sa += a[i];
    rep(i, n) sb += b[i];
    if (sa < sb || (sa - sb) % (n - 2) != 0)
    {
        cout << "-1" << endl;
        return 0;
    }
    v = (sa - sb) / (n - 2);
    int cnt = 0;
    vector<int> p(n);
    rep(i, n) p[i] = b[i] - (a[i] - v);
    rep(i, n)
    {
        if (p[i] % 2 == 1 || p[i] < 0)
        {
            cout << "-1" << endl;
            return 0;
        }
        cnt += p[i];
    }
    if (cnt != v * 2)
        cout << "-1" << endl;
    else
        cout << v << endl;
    return 0;
}