#include <iostream>
#include <cmath>
using namespace std;

long long N, A[1 << 18], B[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];
	if (N == 2LL) {
		long long ans = abs(A[1] - B[1]);
		if (A[1] + A[2] != B[1] + B[2]) ans = -1;
		cout << ans << endl;
		return 0;
	}

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

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