#include <bits/stdc++.h>
using namespace std;
 
#define REP(i, n) for (ll i = 0; i < n; i++)
#define REPR(i, n) for (ll i = n; i >= 0; i--)
#define FOR(i, m, n) for (ll i = m; i < n; i++)
#define FORR(i, m, n) for (ll i = m; i >= n; i--)
#define REPO(i, n) for (ll i = 1; i <= n; i++)
#define ll long long
#define INF (ll)1 << 60
#define MINF (-1 * INF)
#define ALL(n) n.begin(), n.end()
#define MOD 1000000007
#define P pair<ll, ll>


int main() {
    ll n;
    cin >> n;
    vector<ll> a(n), b(n);
    REP(i,n){
        cin >> a[i];
    }
    REP(i,n){
        cin >> b[i];
    }
    ll suma = 0, sumb = 0;
    REP(i, n){
        suma += a[i];
        sumb += b[i];
    }
    if(n == 2){
        if (suma != sumb) cout << -1 << endl;
        else cout << abs(a[0] - b[0]) << endl;
        return 0;
    }
    if((suma - sumb) % (n - 2) != 0){
        cout << -1<< endl;
        return 0;
    }
    ll k = (suma - sumb) / (n - 2);
    if(k < 0){
        cout << -1 << endl;
        return 0;
    }
    REP(i, n){
        a[i] -= k;
        if(b[i] < a[i] or (b[i] - a[i]) % 2 == 1 or b[i] > a[i] + 2 * k){
            cout << -1<< endl;
            return 0;
        }
    }
    cout << k << endl;
}