#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using P = pair<ll, ll>;
using Pld = pair<ld, ld>;
using Vec = vector<ll>;
using VecP = vector<P>;
using VecB = vector<bool>;
using VecC = vector<char>;
using VecD = vector<ld>;
using VecS = vector<string>;
using Graph = vector<VecP>;
template <typename T>
using Vec1 = vector<T>;
template <typename T>
using Vec2 = vector<Vec1<T> >;
#define REP(i, m, n) for(ll i = (m); i < (n); ++i)
#define REPN(i, m, n) for(ll i = (m); i <= (n); ++i)
#define REPR(i, m, n) for(ll i = (m)-1; i >= (n); --i)
#define REPNR(i, m, n) for(ll i = (m); i >= (n); --i)
#define rep(i, n) REP(i, 0, n)
#define repn(i, n) REPN(i, 1, n)
#define repr(i, n) REPR(i, n, 0)
#define repnr(i, n) REPNR(i, n, 1)
#define all(s) (s).begin(), (s).end()
#define pb push_back
#define fs first
#define sc second
template <typename T>
bool chmax(T &a, const T b){if(a < b){a = b; return true;} return false;}
template <typename T>
bool chmin(T &a, const T b){if(a > b){a = b; return true;} return false;}
template <typename T>
ll pow2(const T n){return (1LL << n);}
template <typename T>
void cosp(const T n){cout << n << ' ';}
void co(void){cout << '\n';}
template <typename T>
void co(const T n){cout << n << '\n';}
template <typename T1, typename T2>
void co(pair<T1, T2> p){cout << p.fs << ' ' << p.sc << '\n';}
template <typename T>
void co(const Vec1<T> &v){for(T i : v) cosp(i); co();}
template <typename T>
void co(initializer_list<T> v){for(T i : v) cosp(i); co();}
void ce(void){cerr << '\n';}
template <typename T>
void ce(const T n){cerr << n << '\n';}
template <typename T>
void cesp(const T n){cerr << n << ' ';}
template <typename T>
void ce(initializer_list<T> v){for(T i : v) cesp(i); ce();}
void sonic(){ios::sync_with_stdio(false); cin.tie(0);}
void setp(const ll n){cout << fixed << setprecision(n);}
constexpr int INF = 1e9+1;
constexpr ll LINF = 1e18+1;
constexpr ll MOD = 1e9+7;
// constexpr ll MOD = 998244353;
constexpr ld EPS = 1e-11;
const double PI = acos(-1);

int main(void){
	ll n;
	cin >> n;
	Vec a(n), b(n);
	rep(i, n) cin >> a[i];
	rep(i, n) cin >> b[i];

	ll sum1 = 0, sum2 = 0;
	rep(i, n) sum1 += a[i];
	rep(i, n) sum2 += b[i];

	if (n == 2) {
		if (sum1 == sum2) {
			co(abs(a[0] - b[0]));
		}else
			co(-1);
	} else {
		if (sum1 >= sum2 && (sum1 - sum2) % (n - 2) == 0) {
			ll t = (sum1 - sum2) / (n - 2);
			ll cnt = 0;
			rep(i, n) {
				if (b[i] >= a[i] - t && (b[i] - a[i] + t) % 2 == 0)
					cnt += (b[i] - a[i] + t) / 2;
				else {
					co(-1);
					return 0;
				}
			}

			if (cnt == t) co(t);
			else
				co(-1);
		}else
			co(-1);
	}

	return 0;
}