#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcountll
#define ll long long
#define mp make_pair
#define f first
#define s second
#define Time (double)clock()/CLOCKS_PER_SEC
#define debug(x) std::cout << #x << ": " << x << '\n';
signed main() {
    #ifdef HOME
    freopen("input.txt", "r", stdin);
    #else
    #define endl '\n'
    ios_base::sync_with_stdio(0); cin.tie(0);
    #endif

    int n;
    cin >> n;
    vector <int> a(n), b(n);

    int delt = 0;

    for (int i = 0; i < n; ++i) {
        cin >> a[i];
        delt -= a[i];
    }   
    for (int i = 0; i < n; ++i) {
        cin >> b[i];
        delt += b[i];
    }   

    if (n == 2) {
        if (delt != 0)
            cout << -1 << endl;
        else
            cout << abs(a[0] - b[0]) << endl;
    }   
    else {

        if (delt > 0) {
            cout << -1 << endl;
            exit(0);
        }   

        if ((-delt)%(n - 2)) {
            cout << -1 << endl;
            exit(0);
        }   

        int k = (-delt)/(n-2);
        for (int i = 0; i < n; ++i) {
            if (abs(a[i] - b[i]) > k) {
                cout << -1 << endl;
                exit(0);
            }   

            if ((abs(a[i]-b[i])&1) ^ (k&1)) {
                cout << -1 << endl;
                exit(0);
            }   

        }
        cout << k << endl;
    }   

}