#include <bits/stdc++.h>
using namespace std;

long long N, A[1 << 18], B[1 << 18], P[1 << 18];

int main() {
	cin >> N;
	for (int i = 1; i <= N; i++) cin >> A[i];
	for (int i = 1; i <= N; i++) cin >> B[i];

	// N = 2 の場合
	if (N == 2LL) {
		if (A[1] + A[2] != B[1] + B[2]) cout << "-1" << endl;
		else cout << abs(A[1] - B[1]) << endl;
		return 0;
	}

	// そうでない場合
	long long SA = 0, SB = 0, V = 0;
	for (int i = 1; i <= N; i++) SA += A[i];
	for (int i = 1; i <= N; i++) SB += B[i];
	if (SA < SB || (SA - SB) % (N - 2LL) != 0) { cout << "-1" << endl; return 0; }
	V = (SA - SB) / (N - 2LL);

	long long cnt = 0;
	for (int i = 1; i <= N; i++) P[i] = B[i] - (A[i] - V);
	for (int i = 1; i <= N; i++) {
		if (P[i] % 2 == 1 || P[i] < 0) { cout << "-1" << endl; return 0; }
		cnt += P[i];
	}
	if (cnt != 2LL * V) cout << "-1" << endl;
	else cout << V << endl;
	return 0;
}