#include<bits/stdc++.h>

using namespace std;
using ll = long long;


int main()
{
    int n;
    cin >> n;
    vector<int> a(n), b(n);
    for(int i = 0; i < n; i++)cin >> a[i];
    for(int i = 0; i < n; i++)cin >> b[i];
    ll sum = 0, k = 0;
    for(int i = 0; i < n; i++) sum += (a[i] - b[i]);
    if(sum % (n - 2)) {
        cout << -1 << endl; return 0;
    }
    k = sum / (n - 2);
    for(int i = 0; i < n; i++) {
        if((b[i] - a[i] + k) & 1) {
            cout << -1 << endl;
            return 0;
        }
    }
    cout << k << endl;
}