#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <queue>
#include <bitset>
#include <stack>
#include <functional>

#ifdef LOCAL
    #define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
    #define eprintf(...) 42
#endif

#define rep_(i, a_, b_, a, b, ...) for (int i = (a), i##_len = (b); i < i##_len; ++i)
#define rep(i, ...) rep_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define reprev_(i, a_, b_, a, b, ...) for (int i = (b-1), i##_min = (a); i >= i##_min; --i)
#define reprev(i, ...) reprev_(i, __VA_ARGS__, __VA_ARGS__, 0, __VA_ARGS__)
#define all(x) (x).begin(), (x).end()
template <class T> bool chmax(T &a, const T &b) { if (a < b) { a = b; return 1; } return 0; }
template <class T> bool chmin(T &a, const T &b) { if (b < a) { a = b; return 1; } return 0; }
// template <class T> T gcd(T a, T b) { return b ? gcd(b, a % b) : a; }
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair <int,int> P;
typedef long double ld;

int main (void)
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll n; cin >> n;
    vector<ll> a(n), b(n);
    rep (i, a.size()) cin >> a[i];
    rep (i, b.size()) cin >> b[i];
    ll diff = 0, k;
    rep (i, n) diff += a[i] - b[i];
    if (diff < 0 || (n != 2 && diff % (n - 2))) {
        cout << "-1\n";
        return 0;
    }
    if (n != 2) {
        k = diff / (n - 2);
        eprintf("k: %lld\n", k);
        bool ok = true;
        rep (i, n) {
            ll c = b[i] - a[i] + k;
            if (c < 0 || c % 2) ok = false;
        }
        cout << (ok ? k : -1) << "\n";
    } else {
        if (a[0] + a[1] == b[0] + b[1]) {
            cout << abs(a[0] - b[0]) << "\n";
        } else {
            cout << "-1\n";
        }
    }
    return 0;
}